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:
- Rise Depth: the height from crotch to waist
- 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.
- Rise Ratio: Back Rise divided by Front Rise should be about 1.25 to 1.35
- 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:
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:
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 many pdfs from CKC and VFT):
- 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
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.