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  • Writer's pictureLonda

Saturday Simple Sewing Hint: Key+String Crotch Measuring Tool

The ‘Key’ (no pun intended) to a great pant fit is a thorough understanding of the Crotch Depth and the Crotch Length AND how to measure for each.  

I learned and then have taught for years that one measures and alters for the Crotch DEPTH first, as seen below.  The one thing I see missing in this photo is a string or elastic around the ‘waist’ – or wherever one wants the top of the pant to rest.  That spot can NOT ‘float’ around.  It must be established and defined clearly for and throughout this process.  The way I like to explain the difference is that CROTCH DEPTH is more an indication of skeletal structure, and CROTCH LENGTH reveals the ‘fluff’ (derriere and tummy).

crotch depth

Measuring Crotch Depth

Altering Crotch Depth

Alter for Crotch Depth

Altering the CROTCH DEPTH is done first, because that 0bviously effects the CROTCH LENGTH.


The ‘Key’ that is being shared here is this TOOL for measuring CROTCH LENGTH.

  1. Again, with the ‘waist’ established on the body, take a TOOL like this (long string with a Key tied to the middle of it).

  2. Holding the Tool ‘string’ at the waist in back, bring it between the legs, placing the KEY at that point of your body where you want the inseams to intersect the crotch seam, then bring the string on up around to the waist in the front.

  3. Pinch the string at the waist points, step out of this ‘basket’ measurement, keeping Front and Back defined, and measure –

  4.  from point on string in the BACK to the Key = Back Crotch Length

  5.  from point on string in the FRONT to the Key = Front Crotch Length

crotch length measuring string

Can you see the ‘basket’ created by the Pant?  It’s the ‘basket’ into which your body must fit.  On most of us, the BACK CROTCH LENGTH will be the larger than the FRONT CROTCH LENGTH.  A ‘forward’ located inseam is what European (Burda) Pant patterns are known for.  Doing this creates a larger bias area under the derriere that gives a better fit – is the way I understand it.


Then, of course, their is WEARING Ease.  Unless we are talking about Leggings of knit fabric, there needs to be additional ‘wiggle room’ added to body measurements for wearing comfort.  Here is a chart I found from The Sewing Workshop for what to add.

Crotch Length 1″ – If hips are less than 37″

1½” – If hips are 37″-40″

2″ – If hips are 40″ or more

In general, I always ascribe to the fact that if it is cut in, you can always take it out, but it is harder to go the other way.  Ease is a comfort issue and that cannot be defined by anyone but YOU in the garment WITH the undergarments worn that you will be wearing with the garment.  (A body wearing SPANX will measure and ‘wear’ differently than one NOT wearing SPANX.)


I believe it was Pati Palmer who said one should stitch and fit pants in their underwear and I agree!

The other thing I learned from Pati was to be sure to cut it plenty tall at the top ‘in case’.  Then, to FIT AS YOU SEW, (again with the proper undergarments worn), pull on the pants, and then place an elastic EXACTLY at the location where you want the top of the pants to be, adjusting for comfort and inseam location, etc.  MARK clearly all around the waist.  Doing this is the easiest way I found to adjust for a high hip, fabric ‘drape’, etc.

BITE THE BULLET and just get some basic pants FITTED!

Honestly, during my ‘retail storefront years’ I did so many pant fittings, I really HATE to do pant fittings now.  I long ago came up with my own pant patterns.  It’s worth it to me to keep my body the same so that I don’t need to do it all over again.  However, I’m finding in my Sunroom Sewing Studio classes, that those days are returning.   Since we all wear pants SO very much, it is an important thing to grasp and work through for yourself.   Hopefully this ‘TOOL’ for crotch length measuring will be helpful.

If you have a specific question regarding pant fitting, be sure to put it in the COMMENTS here.  I’ll answer just as soon as I am able.  Many great sewing products are waiting for you at my website:

Come and visit – I’m confident you’ll be glad you stopped by!

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