Cup Sizes for your Derriere : Hummingbird Skirt

Picture 2

Yesterday I showed you what’s going on with the Hummingbird Top pattern linework.  It’s based on plain measurements, without assigning a waist length/waist circumference to a particular bust measurement.  I like this, and I think you will, too.

Hummingbird Blue Top with Hummingbird Orange Skirt

The Hummingbird straight skirt presents a sizing/fit puzzle I’ve been working on for a long time.  Last year, I started a hip-to-waist sizing survey to collect self-reported data on the waist and hip measurements of my readers.  As of writing, I have 700+ data sets.  I’ve returned to these numbers over and over again while I worked on the Hummingbird Skirt.

Start with the Hips

The Hummingbird skirt comes in five base “sizes”: 35, 40, 45, 50 and 55 hip circumference.  Think of it as XS-XL sizing, with customization options built in.

Then the Waist

Hummingbird Skirt K Piece

Each hip has four waist measurement options, which are based on hip to waist ratios gleaned from my data (survey spreadsheets and hundreds of pages of notes).

Click here for a preview of the Hummingbird Skirt Back piece (with adjustable darts) and sizing guide.

No Pattern Will Fit Every Body

Side Seam 2

The biggest fitting issue associated with a straight skirt is the lower back/high hip area.  Among women, waist to hip ratios vary widely.  Further, two women with the same waist and hip measurements might also have very different body shapes in this area.  (Full stomachs, on the other hand, are much easier to predict and accommodate.  This is reflected in the Hummingbird patternwork.)

Waist to hip ratios are a function of an individual’s bone structure and weight distribution, and ruled by other genetic factors such as estrogen levelsScience.  Our bodies are ever-shifting shapes, but ratios have relatively little to do with the individual’s relative weight or circumference.  It’s fascinating.

Picture 14For my Hummingbird Orange and Pink samples, I cut a 40hip and 30 waist.  I was between sizes and opted to start with the next larger set of measurements.

  The Hummingbird Mid-Construction Fit Check shows you how I fine tuned my fit for the closely fitted denim Hummingbird and the less fitted organic cotton twill version.


“Swayback” is a term used in modern sewing and pattern alteration to describe a range of body variations which may or may not have any relation to the actual medical diagnosis of swayback.  Swayback is blamed for creating wrinkles at the lower back.

an illustration of the "swayback" pooling.  Click for an interesting intermediate/advanced pattern geek post on the subject at pattern, scissors, cloth

an illustration of the “swayback” pooling. Click for an interesting intermediate/advanced pattern geek post on the subject at pattern, scissors, cloth

I believe for many people, a swayback issue is less about posture or spinal curvature and more to do with the relative roundness or flatness of the derriere.  Swayback is like an FBA for your bottom.  Think about it…

Whether swayback is posture or a round backside, the net effect is the same.   So is the practical fitting fix, which often involves pinning out darts and extra fabric located in the small of your back.  It’s hard.

Cup Sizes for Bottoms?

Hummingbird About Town

I tend to think about swayback and backsides and so forth in the same geometric/topographic ways I think about breasts and cup sizes and proportion.  Larger bottoms = deeper darts and a curvier waistline seam, just like with busts.  That’s true whether you slash and spread the pattern for an alteration or draft your own.  The Hummingbird Skirt offers cup sizes for your derriere while working to alleviate wrinkles in the small of the back!

Read more at the Hummingbird Mid-Construction Fit Check.

The Virtual Fitting Room

Once the Hummingbird patterns ship and you receive them, we’ll have another 30 Minutes A Day sewalong which means I can work with you on fit.  (We’ll have a Sorting and a House Prize again, too, that was really fun!) I love our sewalongs, and rather look forward to fit challenges in the next one.  I’ll be there with you from fabric selection to cutting to finishing- the sewalongs are like a free online class companion to the pattern.

The Waistband Must Be Mentioned

Simple Straight Waistband

The waistband on the Hummingbird Skirt hits just below natural waist, and is a simple 1″ straight waistband with a lapped back closure.  It is discreet beneath an untucked shirt.  We had a few issues with the Pavlova Skirt waist binding, which sent me back to my drafting board to check and test every waistband length/width for Hummingbird. I also re-visited the method of creating a simple but effective finish at the waist, opting for a narrow straight waistband over the bound edge finish used for Pavlova.

I can not promise to create patterns free of errata any more than I can promise to be a perfect person, but at the end of the day I don’t want your sewing to be a painful experience.  I’m here for you.  Twitter, email, flickr, this blog and   I constantly field questions about fabric suitability and fit, which I enjoy.   I want your sewing to succeed.  I see my role in this as a facilitator to help you achieve your sewing goals.  That’s what Cake is about. (And pockets.)

Tiramisu and Pavlova taught me more than I can express about the process of creating a useful pattern.  During Hummingbird’s production I finally felt like I was in control of the process from beginning to end.  It’s one thing to draft and fit and teach and blog, it’s another thing to start a company.

What do you think?

Please, please ask me questions about cup sizes for your derriere!  I’ve been excited/nervous to show you what I’ve been working on and I’m happy to be challenged or questioned because I am sure about this sizing scheme.  I know it’s different, but I also know we’ll get many great Hummingbird Skirts from this pattern.

Hummingbird Peplum Top & Skirt

Hummingbird Peplum Top & Skirt pattern on Etsy- special presale price only available until April 7!


  1. What a brilliant idea! LOVE!!! I cannot believe you have drafted different waist sizes for each hip – and I had a look at the page on fitting – again – wow! For once I shan’t dread fitting:). So innovative and so cool. You’re a star!

    • Every now and then I write a post and hitting the “publish” button is a little terrifying. :) Thank you, Francesca, that’s the same reaction I had somewhere between the drafting table and the spreadsheets when I was thinking about the challenge of fitting everyone’s skirts via flickr on the sewalong. I’ve been over and over and over it and keep coming back to this, so this is what it is.

      • Well, I totally appreciate all the work that has gone into this skirt, and I can’t believe nobody has ever thought of this – you are so thoughtful. The Amazing Fit patterns try – but hey, slim, normal and curvy? What’s normal? What’s slim? Do we translate them as flat, slightly curvy and Beyonce? Measurements and customised darts – whoohoo!

        • Yes- exactly! What’s normal? Why use all these basically meaningless words, the labels? Measurements… Can’t argue with measurements, right? No baggage in them, right? Well, not like the baggage associated with words like “slim” and “curvy”…

          Thanks, Evie. :)

  2. I love that you have multiple waist sizes for the same hip. Usually it’s not to hard to diy this kind of thing with a multisized pattern but some times the pattern pieces are laid out funky or my hips and waist are in different size packets! I’ve always thought that an FBA for my butt would be super useful!

    • Hehe. Yes, but there’s a little more finesse to it- dart depth and width, waistline angles, etc. But same basic idea, to be sure. :)

  3. Fantastic idea Steph! Cup sizes for Bottoms? Might be a bit confrontational (on the ego side as well ), but a well fitted skirt is better than a poorly fitted skirt. Probably will take a while to get used to the idea, but you are on the right track. I think that the Intimate apparel manufactures should also be using your system, then we might get a pair of undies that don’t ride up your know where, especialy when I can now fit into some of the matching undies for all the different coloured bra’s that I am buying.

    • I can’t wait to try out the blue and orange pieces. Having some body image issues at the moment, seeing some parts of my body that I haven’t seen in decades.It will just take me some time to readjust. Still a fantastic idea , well done.

    • Hehehe! You know I’ve been thinking about bottoms this way for a long time…. I didn’t actually assign “cups” to them, I’m still not sure how that would work, but I think the measurements approach might help keep egos happy…

      And hooray for fitting the matching panties!

      Give me some time to refine it, maybe I make my own clothing line….

      • I do remember doing your jeans class, and stareing at ladies and mens bottoms for weeks. I was only looking at the designs on their pockets, not their actual bottoms,Honest.

  4. I am so excited! I’m quite sure my derrière has a rather large cup size. It makes buy RTW pants nearly impossible to find– especially jeans. (I haven’t tried to sew them yet.). I do have a question actually. Where is the hip measurement taken? I usually measure where my hip bones are widest and allow ease or size on the large side. My mom says that I should measure “at the widest point”. On me, that derrière Maximus point is a couple inches lower than my hips.

    • Yes- do you get that gap at the back waistband? I see that over and over, and belts don’t seem to help much. It comes from having a nicely rounded bottom, I think that’s a good “problem” to have, really, once we can get something to fit you well. My favorite curve on the female body is the small of the back…

      Well- the controversy rages about where to measure hips. I take what I consider a sensible approach, which is to measure at the fullest part of the hip/bottom. Yes, hip depth does come into play a little bit when fitting straight skirts and pants but I find in a practical setting it’s not terribly important because it comes down to a lengthen/shorten issue which is fairly simple to address in a toile fitting…. Even a toile fitting where I can’t actually touch the toile, as it is in our virtual fitting room… The circumference is more important, and the depth of darts and shape of the side seams… :)

      • It will be fun to learn how to do all this! I’ve learnt so much doing the other two patterns both with the sew along. Even the layouts have helped me understand better how garments come together. I’m and engineer, but a beginning level sewist. These patterns are awesome to customize, and also given me hints as to what kinds of fit adjustments I’ll want to learn generally.

        Yes, I do have chronic waist gap. In fact, that is the reason I never wear shirts tucked in and even buy extra long camisoles to wear underneath things to ensure I have a layer over my waist bands.

        • Oh good! I’m glad! I know we covered a LOT of ground with the first two patterns in terms of techniques and concepts, I knew that but hoped the knowledge and techniques would bleed over into the rest of your sewing in a good way. :)

          I think of my work as akin to what an engineer does…. In my way.

  5. I have noticed in the past the waist darts on skirts and realized that in the Big 4 pattern companies the depth and length of the darts do not really change when choosing a different size, just the distance between them. I always wondered how does a dart that is the correct size for a “size 8” derriere also accommodate a “size 16” derriere?? Well, they don’t, no more than a size B cup will accommodate a size DD breast. I began to really understand the geometry and three dimensional structure of the human body when I started learning to draft, but the revelations did not happen when I was trying still to sew solely from pre-fab patterns. Once again, Steph, this is genius! I would much rather take a few measurements and draw a few lines and have a customized pattern BEFORE I cut the fabric then have to cut fabric KNOWING that it will be an ill fitting muslin and I will need to make changes.

    • Yes! You’re so observant and thoughtful, Melanie, and you’re right. I’m really glad you like my idea, and don’t mind drawing in a few lines for a custom fit. It’s simpler than slash n spread alterations, right? And gets the sewist to the same place… There still may be some tweaking of fit that’s necessary (you know!) but I do believe this will help us all get closer to a good fit with less of a collective headache. :) And thank you! It’s nice to wake up to a comment from a clever person calling me a genius… :D

  6. Hey Steph I say just hit that “Publish” button with pride as what you share is always useful, beneficial, fun, informative and helpful in some way or another and at time all rolled into one. I swear you have me in mind for every pattern you design and feel like you are my personal pattern designer (which I’ve also shared on Twitter as you know) and I’m a huge CAKE FAN and love your patterns and love supporting you and your journey through building your company and the huge range of Cake patterns you have coming our way. So my dear special personal pattern designer never fear or get nervous about hitting that publish button as I know there are many more people out there that feel just like I do about you, your patterns and all the wonderful things you share :)

    • Thanks, Chris! I’m blushing! I’m not sure what to do with that kind of carte blanche… Heheh. But thanks, really, it’s good to know the time spent in front of the computer is well-spent and appreciated. :)

      But the computer time *does* cut into the drafting time, there’s the rub! I have too many ideas crowding my head at the moment, and we’ve tamed the production process which means less of my brainwaves go into coordinating and building up Cake, know what I mean? I really need to take a few weeks off blogging so I can fiddle around with the website to make it easier to navigate and get some more designs drafted up! Riffs! Cake does Burda….

  7. I am so, so excited about this pattern. For one, I believe I will utilise the skirt pattern enormously. Fabric type will change the effect dramatically. And I’m loving the peplum top, a great return from the 80s; however, I used it as a fashion item then, not so much as a tummy hider as now!

    Next I am über excited about your sizing design. I loved this in the Tira but the more you explain about the Hummingbird the happier I become. I remember responding to your waist to hip ratio when you first proposed the question. That was quite a time ago. Your research from ‘real women’ looks to have really impacted your design process. I cannot fully imagine the testing involved in trialling these patterns, especially the bottom fullness. How many trials did you have to do to get it right? (Rhetorical question, just so interested). You are in uncharted territory here but have appeared to conquered the market. Congratulations.

    I am still busy catching up with my pavlovas. I must hurry or the next sew a long will be here.

    • I hope you will get lots of use from the pattern, I’ve sewn several wearable samples for myself (I have to get inside the samples, it makes the pattern better…) and STILL have heaps of ideas for variations.

      Peplums for tummy grace- yes! I have the idea of making a striped Hummingbird Dress variation, too. For the Shipping Season when I roll out a few cutting and drafting variations… :D

      Yes, that survey was AGES ago! I thought at first I could pull out an equation showing that waist to hip ratios change in a predictable way as waist or hip circumference increase, but that just wasn’t the case at all. Instead, it turns out we are all quite varied and different. Of course!

      Hmmm… Well… I want to answer your rhetorical question! My first straight skirt sizing scheme was 48 size variations, which I drafted out. I got excited. Then I drafted a plain straight size scheme of 8 sizes. But then I thought about all the fitting we’d do in the Sewalong, and how I really can’t help you pin fit at the small of the back, and considered all the potential pattern alteration for fit posts I’d be making and went back to the varied schematic… I refined it down to 36 size variations, and then down to 5 base sizes and 20 waist variations. Then I started comparing my drafts to my library of corrected Pants Blocks, I have a few hundred from fitting pants on people last year of various shapes and sizes, with the fitting notes. Straight skirts are less tricky to fit than pants, but the side seam/back waist is much the same kind of fitting challenge… I really want to start doing Blocks again, actually, and I think if we have a private Flickr classroom space set up that would work well…

      • I am impressed. Yes it was rhetorical but I definitely am interested to know the processes you have been through. Maybe a book sometime in the future?

        Seeing how you are achieving this method with busts, waists, hips, bottoms etc, I wonder if you are planning a pant pattern including a thigh measurement. You have sort of alluded to it but as this is one of the hardest areas to fit on a women’s body the success you could achieve would be spectacular. I would definitely participate on any private Flickr page to help with the blocks. And as a local if you ever need ‘real’ models I am sure there would be a few of us willing to help.

  8. I LOVE it!!! I had a fleeting thought about derrier adjustments from your last post! I need something for sure! But now FBA has a different meaning (full bum adjustment!)

  9. you really are a genius for thinking about how you can help others achieve a perfect fit! it must have taken ages and a lot of work to compile all of that data, and then turn it into something meaningful…wow. your work is much appreciated.
    knowing that i just have to connect the dots in order to customize your patterns to fit me properly, well, that’s just amazingly helpful!! and if i wasn’t 32 weeks pregnant, i’d be joining in on the sewalong for sure! hmmm, now there’s a challenge for you ;)

    • Thank you! It’s just… I know the pattern fixes, I know the body shapes, so why not just cut out some of the fixes for a simpler sewing experience? But then, I know it’s all a bit different too and wouldn’t want to over-complicate issues….

      Yes! Connecting the dots! In a literal and perhaps less literal sense…

      You know, this is a terrible reason to consider a pregnancy but it has occurred to me if I have a second child I can spent the incubation period doing deep research into pregnancy-wearability/patterns. I suppose I could call the line “Bun.” Hehe. But there’s too much Cake in my head for Buns at the moment…. ;)

  10. Well, the title of this post is a winner! haha And you are so good at thinking outside the box. Love this. I need to do sway back adjustments, but funny enough, my ancient Vogue Sewing book never suggested pinning out the excess fabric. It approached it as needing a larger waist:hip ratio and gives several ways of dealing with it based on the type of skirt/top/dress being sewn – letting out darts, adding width closer to the waist, etc. I have always been very happy with the way their solutions solve the problem, and I think it’s pretty darn similar to your derriere cup size idea, although approached differently. You’re amazing. Keep going, girl!

    • Heheheh! I’m pleased you like it… I had something rather dry in the tiitle line and stuck that in at the last minute because its… ahem… CHEEKY. ;)

      Vogue doesn’t suggest pinning out excess fabric? My mind is blown. That seems the most natural approach to me, I can’t tell you how many skirt and pants I’ve had where I pin out/baste that lower back fabric beneath the waistband, then pin out and baste more, continually tweaking and fussing at times… I figure it’s worth it for a smooth lower back line, but I can see how my pinning-fitting-pinning way is a little cumbersome.

      Yes- there’s many many ways to achieve the same result, my aim is to streamline the process and make it simpler for all parties. :) (And shoot, once the Hbird skirt is out there and we’re playing with it, that means I have a go-to straight skirt base to build y’all all kinds of other lovely skirts..)

  11. This idea is GENIUS! And not confrontational at all, at least not to me – it’s about shape, and the ratios of shapes, not about size. I’m a healthy to slim weight for my height, and I have a curvy bump of a derriere that, as others have mentioned, makes buying pants nearly impossible. Can also I mention that I find the absolute best way to embrace my unique shape is to make clothes that actually fit me?
    Anyway, I was loving how the denim version of this skirt looked on you in the fishing photos, and sighing that it would probably take a lot more fitting work to make it look that good on me – maybe not!! I’ll say it again – genius!

    • Oh good! For all that the approach is different, confrontational is NOT one of the things I want to be… :)

      Yes, you’re so right about embracing one’s body shape through fit. It sounds… So basic, but I think that’s why so many of us find it profound…

      Make sure to poke your head in on the sewalong, I developed this pattern with the assumption I’ll have a lovely ten days of fitting a few hundred skirts on flickr and I’d hate to miss out on that. :)

      • Sounds good! I bought the pattern, but I know I probably won’t have time to sewalong at the same time with you all – I will check out the fitting pictures so I have a better idea when I do get to it. :)

  12. I absolutely agree: You just proved to be a genius – again! I already commented once that I just LOVE your way of thinking, inventing new solutions and thus facilitating the sewing process. Your genius approaches alone are worth buying each and every of your patterns and to spread the word about Cake, so that you can invent and develop even more ideas.
    Maybe you should secure your ideas in some way because it would be a pity if someone else stole them and made money out of your hard work (If a true patent is too expensive: here in Germany we have a “precursor” to a patent that is less expensive and is called “Gebrauchsmuster”, maybe there are similar things in Australia)!
    But please, please invent a different name for the “derriere cup size”, because I have to giggle everytime I imagine to fit my derriere into a bra (sorry for being so direct and childish, but this is the way my brain works ;) ).
    Now I’m even more looking forward to receiving the pattern!

    • Thank you, Malina. I’ll be interested to see how all the fluttering Hbirds suit everyone… I can make samples and juggle numbers and draft draft draft but at the end of the day the proof is in everyone else’s sewing. :) But I believe we’re “onto something” as they say…

      I thought about trying to protect my Intellectual Property, about hoarding and protecting my pattern ideas, some kind of patent but I come back to a few things:
      -can’t copyright fashion, only a label. This is the way fashion works.
      -can a size system be copyrighted? Is it worth the effort/time/money, because a small tweak to a copyrighted system would create an entirely “new” system, even if the concept is the same.
      -can’t copyright a concept. Formulas, yes. Concepts, no.
      -can’t keep the concept from getting out there- the whole point is to put these tools in your hands! And I am sure that will eventually lead to others playing with my sizing and changing it, tweaking it, evolving it.
      -innovators who get widely copied are legends. I’m not a legend at the moment, that’s far too grand, but maybe one day when I can crank out a new pattern like batting an eye and others copy my sizing ideas and we all know where those ideas came from originally.
      -the internet is a giant copy machine. Essentially, I live in the digital online world and sharing innovation is what creates traffic and enthusiasm… I know some people online try desperately to protect “their” IP, but I think that’s an exercise in futility.

      What do you think? Is there an aspect I’m missing? This is just how I think about it, I can be swayed but… It’s nearly impossible to copyright such a thing, I believe.

      And HAhahahahaha! Derriere cups isn’t any kind of official name, it’s more like a way to help the concept “click” for those who are reading… But I LOVE your mental image, that makes me giggle too. hehehe.

      • Wow, thanks for your long and thoughtful reply! Of course I get your point now, I didn’t think of the restrictons, about what you can protect by copyright and what you can’t. Still, the concept is genius, even if you can’t protect it and I just hope that you get the credit you deserve for it! And if you continue like this, maybe one day you will become a legend! So no, I think you didn’t miss anything :)

  13. I love the research that you do to come up with your patterns. Real paattenrs for real women. I am a “Big” girl with a large bust and waist but virtually no bottom so really steer away from fitted skirts as they never fit. I am now thinking that maybe I should give this pattern a go!

  14. You crack me up Steph! Cup sizes for bums :D
    Your attention to fitting variances is wonderful and one of the reasons I love your patterns.
    I, of course, will be needing the large, flat, aging bum adjustment, coupled with the MenoBelly adjustment. (I hope you can stomach the photos I’ll be mailing you heheh!)

    • Hehehe. Thank you, thank you, I’ll be here all week.. ;) Always tip your waitress! *bows*

      Well… Every now and then I fail to fit someone well from photos, but the longer I do it the fewer the fails. And I love a challenge, so go right ahead. :) I’m thinking of building a private flickr fitting room, one that’s not open for all to see, just other sewing people looking for fit advice. But emailing me is fine too.

  15. I think it’s great! It seems obvious now that you have done it, but no one has done it before! Way to go, I am so excited to see how it works in practice.

  16. Oh my goodness! Skirts never seem to fit me properly at both the waist and hip, so your sizing scheme sounds like a dream come true! :) I also want to let you know that I have learned so much from you. I’m making a set of scrubs for a friend, and I just used your dart technique to get perfect darts. :) The sewalongs have been so much fun and so helpful–I do feel like I get a class along with the patterns. And I’m actually sewing instead of just collecting patterns! With your patterns I feel like I get comfortable, useful, cute clothes that actually fit, and whenever I have encountered problems, you and other folks in the flickr group have been so, so helpful. Thank you for all the hard work you put in behind the scenes.

    • I can’t promise it will fit like a glove out of the envelope, but I am sure the fitting process will be smoother… :)

      Oh! I’m so glad the darts are working well for you! I’ve been doing them that way for *years* and it consistently works well on a variety of fabrics… The sewalongs feel like a class to me, too, it has a lot of the same flow and structure. That’s fine with me, I love classes!

      And I’m SO thrilled you’re sewing and not just collecting!! That’s what it’s all about. :) What fun.

  17. As a person who has been doing a FBA as full bottom adjustment in addition to the more common FBA since the age of 13, I think having this fitting variation built into the pattern is a fabulous idea. Go Steph.

  18. This is the most brilliant thing I’ve heard about in a long time. I could use a FBA (full behind adjustment). :-) I love how you are so caring with your patterns. That’s what makes them special. Thanks for all you do.

  19. You’re just getting me more excited about the pattern! I already gave in and ordered a copy, even though I have a good straight skirt pattern. It’s the pockets and how you write about it/approach your designs that sold me! :)

  20. I am looking forward to trying this out based on my unique body proportions. Girl you just may be revolutionising pattern making!

  21. Pingback: Name That Girl Poll, Tins and A Giveaway! « 3 Hours Past the Edge of the World

  22. So amazing! I love, love, love the options for different waist sizes for each hip size. Excellent for the hourglass figure that has much larger hips than most patternmaker ever plans for!

  23. Such a genius idea! I have an ample derriere and small waist and have always had a difficult time with the fit of skirts. I can’t wait to get this pattern!!

  24. Friggin’ brilliant. Way to go.

    I am unfortunately not the target Cake patterns (I haven’t worn a skirt since junior high!), but I love what you’re doing with the patterns. I’ve done something similar in terms of building a basic wardrobe of altered/self-drafted patterns that I make over and over, but it’s taken a long time, and a lot of study and trial and error. Hopefully that will not be so necessary for your customers!

  25. Hi Steph,
    If there were cup sizes for bottoms I would probably be a AAA. With that in mind, for a hip size less than 35 (33.5 to be exact) would I just cut it a bit smaller or is that a bad idea for someone still learning? I’m not sure if I am just trying to convince myself I can make this work because it looks so good on you!

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