How to figure out your rise and crotch depth for pants
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Summary
Want to talk about crotches? Too bad, we're gonna. If the words "rise" and "crotch depth" make you want to lie down on the floor, this one's for you. I get a ton of questions about how to draft the U and the J on pants and jumpsuits, so I broke it down into a few simple formulas. Yes, there's a tiny bit of math involved, and yes, I apologize for that, but it's the easy kind.
Once you've got your numbers, the rest is honestly just "scoot and cut." I'm terrible at explaining things, but I did my best, and by the end you'll have front and back panels that actually fit together.
- Front rise: hips ÷ 4. Front depth: hips ÷ 20.
- Back rise: same as front. Back depth: hips ÷ 10 (twice as deep as the front).
- Want a baggier fit? Use 16 and 8 instead of 20 and 10. Great for cozy jumpsuits.
- Round out the crotch curve with a 1-inch 45° angle on the front and a 2-inch 45° angle on the back, then connect the dots.
- The back is deeper than the front. If you ever forget the math, just lay a well-fitting pant on top, scoot, and cut.
Crotch depth vs. rise (quick version)
Rise is the distance from the waistband down to the crotch seam. Crotch depth, the way I use it in the formula, is how far the curve reaches out into the space between your legs. Heads up: some pattern books use "crotch depth" for the seated measurement (sit on a hard chair, measure from your waist to the seat), which is basically your rise. Same idea, different name.
How to measure the rise on pants you already own
Lay them flat and smooth out the front. Measure from the crotch seam (where all four seams meet) straight up to the top of the waistband. That's your front rise. Flip them over and do the same for the back, which'll be longer.
How do you calculate rise and crotch depth for pants?
Take your hip measurement. Divide it by 4 for the rise (front and back are the same), by 20 for the front crotch depth, and by 10 for the back crotch depth. The back is twice as deep as the front because that's where your butt goes.
| Measurement | Formula | Example (44 in hips) | Baggier fit |
|---|---|---|---|
| Front rise | hips ÷ 4 | 11 in | 11 in |
| Back rise | hips ÷ 4 | 11 in | 11 in |
| Front crotch depth | hips ÷ 20 | 2.2 in | hips ÷ 16 = 2.75 in |
| Back crotch depth | hips ÷ 10 | 4.4 in | hips ÷ 8 = 5.5 in |
How do you draw the crotch curve?
- On each front and back panel, measure down from the top by your rise (11 in in the example) and mark it.
- From that mark, measure out by your crotch depth: 2.2 in on the front, 4.4 in on the back.
- Your crotch isn't L-shaped, so round the corner. Draw a 45° line 1 in long into the corner on the front, and 2 in long on the back.
- Connect the dots in a smooth curve from the rise mark, through the end of the 45° line, to the depth mark.
- Want the front lower than the back? Move the front rise mark down a bit. This is a starting point, not a law.
What if I don't want to do the math?
Lay a pair of pants that already fits you on top of your fabric, line up the crotch curve, leave an inch or two of seam allowance, and cut. Scoot and cut.
FAQ
What's the difference between rise and crotch depth?
The rise is how far down the crotch point sits from the waistline. The crotch depth is how far the curve reaches out past the side of the panel, into the space between your legs.
Where is the crotch on pants?
It's the point where the inseams and the center front and back seams all meet.
How do you measure the rise on pants?
Lay them flat and measure from the crotch seam straight up to the top of the waistband. Do the front and the back separately; the back rise is longer.
Why is the back crotch deeper than the front?
It has to wrap around your butt. That's why the back depth uses hips ÷ 10 and the front uses hips ÷ 20.
How do I make jumpsuits or lounge pants baggier?
Divide by 16 and 8 instead of 20 and 10. It gives you more room in the crotch for cozy pieces.
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Transcript
Hi. Hello. Want to talk about crotches? Too bad, we're gonna. I get a lot of questions with the jumpsuits and the pants about how do I do the U, what does my J do. I have some formulas to make it a little easier. There is some math involved and I would like to apologize for that. I hate math, but it's kind of a part of sewing, so we've got to deal with it. All right, get ready to figure out your rise and crotch depth. You have some simple equations. For the front rise, you're going to take hips divided by four. And for the depth, you'll take hips divided by 20. On the back, same for the rise, but for the depth, you want it twice as deep, so instead of dividing by 20, you divide by 10. You could also measure using 16 and 8 for a baggier fit, for the jumpsuits, some cozies. That's what you'll use.
You have four pieces: two front panels, cute sides kissing, and two back panels. Take your hip measurement, divide it by four. Let's say your hips are 44. That equals 11. So you come down 11 inches on the front and the back. 11, 11, make a wish. Then for the depth of the front, hips divided by 20: 44 divided by 20 is about 2.2. And on the back, you do it where it's twice as big, so 44 divided by 10 equals 4.4. So 4.4 this way, 11 in this way, 2.2 this way, 11 in this way.
Your crotch is not L-shaped, right? So on the front side you draw a 45° angle that is 1 inch long. On the back side, you do 2 inches at 45°. Now you connect these. You go boop boop boop boop boop, and then boop boop boop boop. When you round it out like that, you now have a more rounded shape, so the two pieces will go together and work. You might want your front lower than your back; if that's what you're aiming for, you can bring it up further or drop it lower. This gives you a general idea of where to start.
A lot of times pants will come in more right here like this. See how this one's coming under? Make sure you've got an inch or two, then cut the extra off. You'll see this one is much deeper than this one. That's your back, that's your front. So that's as easy as no math: just scoot. Scoot and cut. Tada. It's that easy. I hope this helps. Let me know. Like, subscribe, and smash all the buttons or whatever I'm supposed to tell you. I love you. Thank you. Goodbye.
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