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Fit the Seat of Your Pants

Measure your derrière, then revise the back pattern

Threads Issue #212, Dec. 2020/Jan. 2021
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Many people experience problems with store-bought pants fitting correctly in the seat, waist, and hip areas. Bodies come in many shapes and types, and your waist-to-hip proportion may not match the garment’s cut. A common issue is finding pants that fit comfortably in the hips, only to have a gaping back waistband. Alternatively, if the pants fit your slim waist, they can hardly be pulled over your hips. The opposite situation exists, too, when your hips and seat are proportionally small compared to your waist. This results in excess fabric over the buttocks and back thighs.

For many sewers, the same fit challenges occur in commercial pants patterns, so making your own pants doesn’t immediately solve the problem. Fitting a pants muslin is tough to do on your own, especially if you’re focusing on the rear view. However, you can accurately adjust a pants back pattern based on your measurements. I’ll show my slash and spread (or close)technique. This simple adjustment alters length and width, both of which are involved in fitting a fuller or flatter derrière. 

You’ll cut the pattern along a set of prescribed lines, then pivot the resulting sections to add or subtract fullness where you need to. Once you try this pattern-based approach, you can personalize the fit of any pants pattern you choose.

Pattern Fit Pants How to fit the seat of your pants

Record essential measurements

Put on close-fitting garments, such as leggings or tights, but be sure they don’t compress your body. Measure the body, then measure the pattern. Begin with a pattern that fits you well at the waist. In the process of adjusting the pattern, you’ll enlarge or reduce only the back pattern to fit.

Body dimensions

Waist: narrowest part of the torso.

Hips: fullest part of the hips or thighs.

Hip depth: distance from the waist to the full hip, at the side seam.

Vanessa Nirode is a tailor for TV and film costumes. Look for her patterns at

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  1. User avater
    neucarol | | #1

    Happy to see a photo of what good seat pant fit looks like. However (always has to be a 'However'), the fabric print makes it difficult to see if there are sure there are not.😎
    This is a much better solution to most seat alterations that are just a slash and spread which results in all crotch length at waist and skewed grain line.
    Do have a question about the location of line A where hip width is adjusted. The width adjustment is several inches above the hipline where the extra width is needed. Since the photo shows a nicely fitted seat, please explain why this works.
    One other question concerning the Crotch Line...what if the Crotch Depth is more or less than the line across the pattern from the crotch point? Assuming Crotch Depth is altered with Hip Width?
    Thanx for this in-depth article to add to my fitting knowledge.

    1. CarolFresia | | #2

      Hi, NeuCarol,
      Good questions! And yes, the pants fit the model well, though the print does make it a little hard to see.
      Line A is located 1 1/2 inches below the dart point, and in this case it enabled the pants to be expanded to add length and width where the model needed it without unduly lengthening the dart. If you want to experiment with placing line A a bit lower, and make a longer vertical cut through the dart, you can try that. The resulting dart might be longer than you need, so I'd suggest pinning it to fit.
      The crotch depth is adjusted when you spread at line A. It's worth making a muslin, or a wearable muslin, once you've adjusted the pattern. Each body is individual, and you may want to tweak the darts, waist level, etc.
      Carol J. Fresia, Senior Technical Editor

      1. User avater
        neucarol | | #4

        I disagree that line A added width where needed. Hip width is needed at hip line, not below the dart point.
        The principle of fitting is to adjust at the point of need.

  2. Shana0127 | | #3

    Let me add my frustration with the photograph of the finished pants. While I'm sure they fit the model well, it's almost impossible to tell given the print of the fabric. It would have been much more helpful if you'd included another photo of the revised muslin, with the horizontal lines etc. so we could actually tell what it looks like after the adjustments were made.

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