How To,  Sewing Tips

Crotch Width: What Causes Crotch “Smiles”

Fitting pants is challenging because the patternmaker must coordinate SHAPE to MEASUREMENTS to MOVEMENT (sitting, walking).

Previously I’ve blogged about CROTCH SHAPE,

  • the angle of the Front Rise and Back Rise
  • the shape of the “hook” going under the crotch.

This time I’m concentrating on RISE MEASUREMENTS.  The patternmaker must establish the correct balance between 4 interconnected  measurements:

  1.  Rise Depth: the height from crotch to waist
  2.  Rise Length : the measurement from center-front at waist, down under the crotch, up to the center-back at waist.  This is divided into  Front Rise and  Back Rise.
  3. Rise Ratio: Back Rise divided by Front Rise should be about 1.25 to 1.35
  4.  Crotch Width:  the “empty” horizontal distance between the Front Rise and the Back Rise, measured  at  2″ above the crotch, resulting from the “extension” of the crotch curve at the inseam (what they called “crotch hook” when I worked at Victoria’s Secret).


If this balance isn’t met, the result will be what industry calls “Smile Lines” (upward wrinkles and pulling) or “Frown Lines” (downward wrinkles and pulling) at the crotch area.

You are probably very familiar with the first 3 measurements:

1. Rise Depth can be measured on your body with a ruler, by sitting in a (non-cushy) chair. Compared to your pattern, this tells you if the pants will be the overall rise that you like: high-waist, natural waist, low-waist:

crotch depth….depth


2.  Rise Length (or Crotch Length) can be measured on your body with a bendable ruler, or a string. Compared to your pattern, this tells you if there will be enough room to go over your belly and bum:

……crotch length….fbrise


3. Rise Ratio: how much of the total rise is in the front, compared to how much is in the back.  You can measure  front-to-back rise ratio on your body by putting a simple weight (like a metal washer) on a string, holding the string from your belly-button center-front down under your crotch up to center-back, and letting gravity pull the weight down to the lowest point (easier with a helper!).

On the  pattern, rise ratio can be calculated through basic division:

  • Back Rise divided by Front Rise : hopefully somewhere from 1.25 to 1.35

For example, pants with one pattern piece, cut same for front/back (example in photo is the Fiji Sun Suit by Whimsy Couture which has just a “crotch cutout” piece, same for front and back….other examples are CKC  Taylor and VFT Daphne):



  • Back Rise divided by Front Rise will equal 1.0 ( bunching in front, biting in back)

But even pants with a nicely shaped Front Rise and Back Rise will have fit issues if the ratio is off (Cali Faye “Tulip”):


  • Back Rise 9″ divided by Front Rise 8″ = 1.125 (needs more length in Back Rise)


You may be less familiar with the 4th measurement:

Crotch Width is  the horizontal distance between the Front Rise and the Back Rise,  measured  at  2″ above the crotch on the pattern. This is an “empty” measurement on the pattern, and it’s really hard to measure on your body, which is probably why it’s the #1 reason that pants often don’t fit well.

(Edited to add: I just learned this from a blog-reader:”As a doctor, I think I can give some insight to the crotch width measurement. It is the front to back distance between the pubic symphysis and the ischium.”  Wow, who knew?  It CAN be measured!)


A well-designed pant, with Crotch Rises drafted using  a French curve into a nice U-shape, will automatically have a Crotch Width that fits well: no “crotch bite” in front, no “wedgies” in back. A rule of thumb is that Crotch Width should measure about:

  • 6″ to 7″ in adults
  • 5″ to 6″ in childrens
  • 4″ to 5″ in toddlers


(illustration: (

Crotch Width is something I never studied in design school. Only when I got into manufacturing did I discover the impact of it: factories would try to squeeze the marker (the whole configuration of all the pattern pieces for all the sizes) as tight as possible to save fabric/money, and the easiest way to do that is to skimp on the points that stick out.  If the Tech Designer does not indicate Crotch Width on the specifications, the factory can get away with this by slightly shifting the thigh width from inseam to outseam: same thigh measurement (which always gets checked for production approval), different Crotch Width shape (much more difficult to measure for production approval).


When I moved to  Tech Designer at Victoria’s Secret, I learned that they consider Crotch Width a critical element of establishing fit of pajama pants, and it was always included in the specs. Now it’s “second-nature” to me, which is why I cringe whenever I see pants with a “V”shaped crotch that fit poorly and cannot be comfortable: the Crotch Width is too small.

Compare these 2 patterns by Avilo Charlotte (Crotch Width measured 2″ above crotch):


  • left is “Bubble Shorts”: crotch width 3.5″
  • right is “High Tide”: crotch width 4.25″

Both are small-ish  in Crotch Width, but the one on the right is a better fit.

The most common fitting issue that I see in pdf pants patterns is Smile Lines. The cure for Smile Lines is to increase the Crotch Width measurement, by extending the “hook” (extension) of the Front Crotch Curve and Back Crotch Curve, also referred to as “adding width to the inseam”:


For a detailed  explanation, I highly recommend the  Pati Palmer book  “Pants for real People”:



A more extreme case of  “smile lines”” is called “whiskering” or even “diaper-front” or “crotch bunching”: this is caused by a combination of

  • too short Crotch Width (needs more extension to the front hook to create a wider U-shape)
  • too small ratio Back Rise to Front Rise (front rise needs shortening, back needs lengthening).

This creates a “bubble” in front of the crotch, on top of “whiskers” to each side. You can see it in many tester photos of shorts and pants pdfs. I discussed this in a previous blog post.


So, if you’ve ever had issues with “smile lines” when fitting pants or shorts, take a look at the pattern and check to see if the problem is a too-short Crotch Width. If it is, try adding more extension to the Crotch Curve. This may require shaving off some from the outseam, so that the amount of fabric going around the thigh doesn’t get too baggy.

Happy Sewing!


  • Melissa

    Thank you yet again for explaining problems I have seen and been frustrated by, in such a way that even a novice can see how to at least where to start in fixing it.

  • Diane Cullum

    Great post, but when I add to the crotch curve to avoid butt smile, the high thigh area has way too much extra fabric.

  • Rita's

    I love this. It is so informative. As a doctor, I think I can give some insight to the crotch width measurement. It is the front to back distance between the pubic symphysis and the ischium. It’s taken two inches in to allow for ease of movement as well as the soft tissue covering.

  • martina

    I get close to a really good fit, and then I get a weird little bump of fabric directly over where my legs meet my body…I think they call it a keyhole. What IS it? Is there any easy way to get rid of it?

  • Sue Short

    I have made a file to keep all your tutorial in. I have had to refer to them already. I’m work I g on shorts right now

  • Dawn B

    @Martina and 7pinedesign, after reading the 1ststeptosewingsuccess link, aren’t they referring to “camel toe”? (yuck! I loathe that term)

  • Amy C

    Does a person with a large belly need a larger crotch width? I’m having trouble visualizing it. Thanks!

  • Jillayne

    When I’m measuring the crotch width of a pattern, do I measure where the points of the pattern are touching or overlap to account for the seam allowance? Some of the photos have the measurement taken when the points of the inseam are touching and some have the seam allowance folded back before measuring the crotch width. I’m trying to make pants for my daughter because all the pants from the store are ‘uncomfortable’. Hoping I can learn what makes them uncomfortable and how to make well fitting ones because this complaint has been going on for years and is driving me crazy!

  • [email protected]

    That’s my mistake if the photos are wrong, it should be measured without seam allowance, in other words what the finished width will be after the pants are sewn. Does your daughter have ANY pants that she finds comfortable? Or at least less uncomfortable? My own daughter has sensory issues so we’ve been through some struggles. One idea I’ve used is to analyze her clothes on laundry day: whatever has NOT been worn are the least favorites, so I try to figure out why. I’ve finally found one brand that she likes, but it wasn’t an easy process.

  • Jillayne

    Thanks! Sorry I didn’t see this for forever and then was always looking at it on my mobile and hate making comments from my phone. She has me stumped because what use to be comfortable isn’t anymore. And the size up in the same brand doesn’t seem to do it. Usually if she wears the clothes for an hour, then she’s fine. It’s getting her to do that without me pushing her into it. I tried making her pants from the Maxxine Pants by Love Notions. Not crazy about the results. I did end up widening the crotch width using your tutorial and it was probably the most successful pair as far as comfort for my daughter. But there seems to be bunching in the front I don’t know how to get rid of. I blogged about it at Thanks for your blog. I love reading your posts and have a greater desire to raise the level of my sewing and fitting after reading your posts.

  • [email protected]

    It really is a matter of trial-and-error…and sometimes fixing one area only creates an issue in another. Have you tried using the Palmer-Pletsch pants-fitting book? Many libraries have it…it has the best tips I’ve seen for “tweaking” pants fit.

  • mlh

    Some of the pictures show the front to back rise shape with the edges of the pattern just touching and the front and the back vertically straight (with grain lines vertical). A couple of the other pictures have the front and back leg seams butted next to each other as they would be sewn together. Which method is the correct one when reshaping the crotch shape?

    When the front and back leg seams are butted against each other (as the first picture) the rise shape looks like a W where the front meets the back. Should this be smoothed out to create a U shape?

    Thanks for your insight and help with this. I hadn’t heard of the Crotch Width measurement before, but it makes sense. I’ve been trying to make perfect fitting pants made for years, so going to check these measurements tonight. Right now I have a pant I’m trying to get right and I’m on the 4th muslin. I’m still getting an issue with the back rise pulling forward towards the front which gives the appearance of a wedgie, which isn’t very flattering. Looking forward to trying these new tips out. I’m going to extend the back crotch extension and check the depth and also check the front to back ratio…

  • [email protected]

    Very observant! The 2 different measuring methods came from 2 different textbooks that I have from 2 different classes at FIT. I’ve seen both methods used at various manufacturers I’ve worked with. So to answer your question, neither/both are ‘correct”. That’s why design is an art, not a science.

    Same situation with how to “spec” a garment: every company I’ve worked with has their own detailed specifications manual. Some say that you measure sleeve length from shoulder, others from center-back. Some measure garment length from mid-shoulder, others from high-point-shoulder. Some companies measure chest at the underarm, others 1″ or even 2″ down side-seam from underarm. Some businesses measure hip at 5″ from waist, others 6″ or 7″ from waist.

    There should never be a “W” when stitched: that picture with the pattern edges butted would look like a “U” if the sewing lines were butted.

    Perfect-fitting pants are indeed the holy grail of pattern-making, because so many factors are involved simultaneously (rise depths, angles, and shapes)…plus movement (sitting, walking). I’ve seen manufacturers go through 20+ fittings for a single pant style….the only other apparel item that I’ve seen getting so much finessing is the bra (again because of multiple factors each affecting the other). In general, wear your muslin around your home, slash-and-spread wherever it’s pulling, pin out excess wherever there’s too much fullness. And know that you are in good company!

  • mlh

    Thanks for taking the time to respond and help clear up my confusion! Would you mind sharing what book the first image is from? I’m always on the hunt for insightful pattern making books. Also would it be possible to blow up the 2 images from “Pants for real….” ? I’m curious to see the text/explanations.

    Yes, it seems to be that patternmaking is definitely an art. There’s no one way to do anything and no guaranteed results. I’ve worked with many professional pattern makers and to be honest most seem to be “winging it” even after 10-15 years of experience- it really is trial and error.

    I checked my patterns and my crotch width was just under 7″. The back to front ratio was at 1.35 (just slightly over). So I think I’m good on the numbers, but the back rise is still pulling forward creating a wedgie affect. The length of the back rise is long enough (comparing to other pants). I’m going to extend the crotch extension (3/4″ at back, 1/4″ at front) to create more of a U shape at the bottom, right now the straight area (bottom of U) looks fairly narrow. I’m also going to fill in also where the back rise hooks at the bottom (shallower curve/less tight) to give more fabric there.

    Yep, it’s great to hear everyone else’s struggle with getting pant fits right- make’s me feel less incompetent and more normal:)…haha…I guess that’s why it’s also so hard to find great fitting pants off the rack- it really is art!

    Thanks again for the post and help clearing up questions!!

  • [email protected]

    Unfortunately I’ve given most of my textbooks to my daughter’s friend who just started her fashion degree at Kent State….I did scan the full page from the Palmer/Pletsch book and added it to the blog post. I haven’t figured out how to get high-res pictures in WordPress, so I’ve emailed the scan to you. The book is geared towards women’s-wear, but many of the principles apply to mens-wear (although women have more shape weirdness due to what pregnancy does to our bodies).

    One reason you’ll find so many differences between patternmakers is due to the difference between draping and flat-patternmaking. Most people have an affinity for one over the other. Numbers-oriented people tend to prefer flat patternmaking because it’s all about reasoning and calculations…visual learners usually like draping better: go straight for the muslin and the dressform, numbers be damned, if it fits, it’s correct. In the end, you need both methods combined (either start with draping, then true the pattern when flat…or calculate the pattern on paper, then transfer to muslin to check the fit in 3-D)…but the difference in approach is what makes it appear like “winging it”. And with pants, since there are so many elements affecting each other, it sometimes IS a matter of trial-and-error.

    Also sometimes with pants, the adjustments may seen counter-intuitive: people sometimes scoop out more from the crotch curve, when what’s really needed is to fill in more: as you said “to give more fabric there”. It sounds like you are on the right track. Another option is to spend an afternoon trying on tons of RTW in a shop with good 3-way mirrors. Nobody will know if you bring a camera, even pattern-tracing paper, into the dressing room. Every major manufacturer uses their own dress-forms (sometimes they name them after their favorite fit-model) which is why there is so much variety of shape in RTW. If you find a brand that fits, you can study it to find out what the “secret sauce” is!

  • mlh

    Thanks for uploading the larger pic and the advice/insight!

    Yeah, I think my impression of “winging it” is probably a result of there being “more than one way to skin a cat” when it comes to pattern making and fixing fit issues. I like anything really, everyone has their own ideas and ways to fix problems. I guess I fall more in that mathematical group in the sense I wish there was a specific formula/instruction for every fit issue that would resolve that issue. Like you’ve said before pattern making is like an art and requires trial and error.

    Good idea on studying pants that I like the fit on….I’m going to spend some time on this as I work on making the perfect fitting pant!

    Thanks Again!

  • [email protected]

    You’re so welcome! The future will probably bring more 3-dimensional imaging programs that let you stand in a CAD box to be personally measured for unique patterns, and all of the trial and error may go away. Until then, yes it’s definitely a lot of trial and error. Best of luck to you!

  • margo

    “This may require shaving off some from the outseam, so that the amount of fabric going around the thigh doesn’t get too baggy.”

    Can you clarify what the “outseam” is? I can’t get rid of crotch smiles/whiskers and it’s making me nuts.

  • [email protected]

    Hi Margo, outseam = sideseam. Sometimes when you add to the rise (depending on the pattern shape) it can add too much fullness to the thigh circumference, so you need to pin in some of the fullness from the side-seam. It does take a lot of experimentation to get pants right.

  • Alexandra

    Hello in my case am a little bit confused with the rise length and the rise ratio
    I read sum where to get the correct front rise ratio and the back rise ratio you have to divide the rise length into two and then take two ihes from the front and add it to the back.example: my rise length is 26.divided into 2 is 13,so now front length is 13 n back length is 13,so u subtract 2″ from the front leaving u with 11″ and adding it to the back to get 15″. It works fine,but coining across yours I want to learn and understand
    How do u measure and calculate yours to get the 1.25 difference

  • [email protected]

    Hi Alexandra! It’s not an exact calculation, that’s why I wrote 1.25 to 1.35. So much depends on the individual body….some of us have more belly, others more bum. Also the garment styling: classic Levi’s original bluejeans, for example, have a lower-sitting front rise and a higher-sitting back rise (if you look at a person wearing them, from the side, the waistband is at an angle dipped n the front). Other styles are much more horizontal front-to-back so the ratio would be smaller. In general, I find that indie patterns tend to use too short of a back rise and too long of a front rise.

  • Kim Schellenberg

    Re: Dr. Blogger & anatomical markers. THIS is Exactly the kind of info that I am looking for: everyone has these physical points of reference! My BIG question is in regards to the placement of the inseam along the crotch, ie) Rise Ratio.

    I deal with Chronic Pelvic Pain and have given up trying to find pants that fit. By the time I have tried on a few pairs of ill-fitting pants, so many pain trigger points have been activated that I hurt for days! Determining the intersection of inseams and crotch seams is critical, for sitting on an ill-placed mass causes misery. If the Dr. could indicate where that spot is along one’s undercarriage, it will make pants fitting simple, for every woman knows where it is on her anatomy!

    Please, please ask: it is estimated that 10 million women deal with Chronic Pelvic Pain – that is a lot of people whose clothing issues are a serious concern!

  • Mandy

    Thank you for this article. Had never heard of the Crotch Width measurement. My question is: you mention that the crotch width is taken 2” above the inseam intersection – so how does widening the ‘hook’ help, when it is 2” lower that where that measurement is taken?
    Otherwise, I’m now keen to get my old pants pattern out and measure the pieces before starting a new muslin. The first muslin fit on the hips, but was hideously oversized everywhere else, except the crotch was ‘puffy’ above the intersecting crotch seam but had upward ‘whiskers’ as well. Truly a nightmare! (Since quitting smoking and gaining too much weight!)
    Kind regards from Australia.

  • [email protected]

    Hi Mandy! Congratulations on quitting smoking! My mum quit “cold turkey” (just stopped one day completely) after smoking a pack a day for 30 years, so I know it’s possible…but still an enormous challenge.

    As for the crotch width, try it out on a piece of paper: draw a (miniature) front pants pattern piece with the side-seam on the left, then a back pattern piece with the side-seam on the right, with crotch points touching. Now cut the paper in half vertically where the crotch points meet. Pull the two paper pieces apart slightly to show the effect of adding to the crotch “hook”…and you’ll see that the crotch width is increased by the exact same amount.

    I wish I could put illustrations in comments….if this is hard to visualize let me know and I can send you an email.

    And I highly recommend investing in one of the pants fitting books in the post…well worth it in my opinion.

    Best, Janet

  • Zosia


    This is so useful information. I am always looking for extra info on making pants perfect to the body.
    Fitting pants is always a challenge for me. I saw you’re picture about “what to do …if ” (with the blue drawn pants ), looks from an old book. Do you know the name of this original book?
    Under this sketch/picture you mention the Pati Palmer book, but is this from that book or another one?

    Thank you so much!
    Greetings Zosia from Holland

  • [email protected]

    Hallo Zosia! My husband is from Eindhoven, his brother lives in Amstelveen, my niece and nephew attend university in Rotterdam, and my in-laws live in Mierlo !

    Sorry to say, I do not know the source of the vintage illustration…I found it on Pinterest, but I don’t know where the original is from. I definitely recommend the books from

    Best regards from the U.S.!

  • Autumn G.E.

    The “bubble” above the “whiskers” seems to be the main conflict in the pilot episode of the comedy show “ Curb Your Enthusiasm,” this is darkly amusing – to see the underlying causes of such an embarrassing pants issue!

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