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Fitting Back Crotch Curve

AnneAudette | Posted in Fitting on


I’m fitting shorts.  They feel very comfortable but the back looks bad!  I’ve taken in the CB seam quite a bit.  How do I eliminate the wrinkles and other distortions?  Looking at the photo, the shorts may be a little too snug.  Please comment!

Please see photo…





  1. Tatsy | | #1

    HI Anne,

    I couldn't get the pix to come up, but I've struggled with this problem for years.  It usually means that there is too much material in the CB and not enough length (width?) in the crotch seam.  Don McCunn has a trick in his book How to Make Sewing Patterns where you take a lightweight coathanger and bend it to get the shape of your torso front to back, then make a template to lay on top of the pattern to show you how much to cut out of the pattern.  For years, I struggled with adding to the crotch at the inseam when I actually needed to take more out of the back.  If you're worried, try it on a muslin first.


  2. fabricholic | | #2

    Hi AnneAudette,

    I measure sitting down on a hard surface with a 12" ruler, the crotch depth. Measure from the surface to the top of your waist, sitting up straight. You need to add how much ease you want to that number. I usually add 1" ease. I measure the crotch length with a measuring tape, from the front waist between legs to the top of waist in the back. Don't move tape just yet. From the front waist down to where your seam is, take that measurement, then from there to top of back waist, and take that measurement. Alter your pattern to these measurements. Does that help? I can't see your pictures either.


    1. AnneAudette | | #3


      Thanks for the responses.

      The shorts were taken from a pattern I made and fit to myself.  I've lost weight since I made the pattern.  The front fits a lot better.  Here's a photo...

      I apologize for the other photo...



      1. Ralphetta | | #4

        It appears to me that you you've taken a little too much out of the side seams.  I think you just need to lower the crotch seam and let the sides back out, like others have suggested. 

  3. cat42 | | #5

    It looks to me (from your photos) that the shorts are too tight across the fullest part of the buttocks. I deduce this from the mostly horizontal wrinkles from the side seam toward the buttock.

    The diagonal wrinkles from the buttock down toward the inner leg may mean you need a deeper crotch, but I'm not sure. And the crotch depth may not be quite deep enough. I often have these wrinkles, too, and cannot always get them to go away. They are a puzzlement. Hmm, using the rule that wrinkles "point to the problem", these point to the inner thigh. Perhaps you need to make the inner thigh seam more vertical on the back leg? I think this is called a knock-knee adjustment.

    However, try doing an enlargement for a large derriere (not that you have a large derriere, but yours is slightly bigger than the pattern). That enlargement will also lengthen the crotch depth a bit as well as add more width at the inner thigh at the crotch. You don't need to add much width, perhaps only a half inch or less.

    There were a couple articles on "fitting pants from the waist down" in Threads. The first article needed some clarification, hence the second one. They do give a good description of how to make the changes you need.

    1. AnneAudette | | #6

      Hi, cat42:


      You are so right on!  I worked on my shorts last week and realized there is a lot going on at the inner thigh.  I did change the crotch curve with minimal results.  Then I began to think about my thighs touching when I stand straight.

      The shorts are out in my sewing room yet in the back of my mind.  I've been super busy.  I think of them often...  I will get them fitted properly.

      Thanks for bringing the Threads articles to my attention.  I have them all.  Fitting is new to me  so it takes me a awhile to understand the wrinkle solution.

      I really appreciate your post! 

      Thanks again,


      1. cat42 | | #7

        You're welcome.I am very knock-kneed; my inner legs touch all the way from the crotch to the knee when I stand straight, and they rub together miserably when I walk. To straighten the curve at the inner thigh, here's what I do:Slice across the back leg pattern at the knee. Slide the lower leg over toward the inner side until the inseam of the lower leg almost lines up with the point of the back leg crotch. Then using my long french curve, I draw a new, almost straight line to connect the crotch seam/inseam point to the lower leg inseam, and then I add the seam allowance. The side seam then needs to be trued using a french curve to draw a new seam line from the hip or crotch depth line to the knee.Then I do the same with the front leg.Now I walk the seam of the front leg inseam along the back leg inseam, to see if they still are about the same. The back should be a little shorter from the crotch point to about halfway down the inner thigh, so that it has to be stretched a bit to match the front leg (this helps the pants to curve under the derriere). If more length has to be added to one or the other (usually the back), I do it where I sliced the pattern at the knee, pivoting at the sideseam and moving the lower leg outward slightly. This works for me because my lower legs go outward below the knee.Cat

  4. DONNAKAYE | | #8

    I think I see your picture well enough, so let me give this a try.

    I don't think your problem is in the thigh, as your inner thighs don't look disproportionately large for your figure.  Actually, I think the drag lines point to the hip, both at the upper waist and at the seat.  In other words, I think a simple hipline alteration will give you the cure you're looking for.

    Try ripping out the pants above and below the hipline drag lines and open then up, letting them release.  Pin the garment to you at the opened seams to an undergarment such as your underwear, creating V's.  If the drag lines disappear, you've got a simple hipline alteration.  In other words, you've got more flesh than the pattern calls for at the lower hipline, and you're also a bit fleshy right underneath the waist.

    I've attached a crude drawing of what I'm talking about.  If this doesn't do it, then another suggestion would be to straight the grain at center back and then work from that point, because I really don't think you're going to solve your problem as long as center back is off grain.

    Sorry, I'll send another message through with the diagrams.  Forgot to attach it to this one.....

    Edited 8/9/2007 9:16 am ET by DonnaKaye

  5. DONNAKAYE | | #9

    Okay, attached is the drawing.  Let me know if you understand (or don't understand) what I'm doing here....d.

    Edited 8/9/2007 9:19 am ET by DonnaKaye

    1. AnneAudette | | #10

      Hi Donna:

      Thank you for both emails and especially the drawings.  I'm really intrigued with your findings.

      I see I have a lot more work to do, and, that's okay!

      I'll keep all of you posted as I progress.

      Thank you very much.


      1. cat42 | | #11

        Just FYI, its possible to have inner-thigh fitting problems, even without having large inner thighs (I speak from personal experience). People with knock knees have no space between their thighs at the crotch, when they stand straight. In her photo, Anne is standing with her legs apart, so you can't see her inner thighs touching. That said, you may still be right about needing more room in the hip, especially since she has the horizontal drag lines from the side seam at the hip. Interesting method of pinning to undergarments. I live by myself, and spend a lot of time alone, especially when sewing, so I have no one to help me with fitting issues. Pinning to undergarment is a great idea.

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