Pattern alterations: How to adjust the crotch in pants

Over the past couple of months I’ve been working on a series of leggings patterns for girls and women (you can find them in the Cucicucicoo Patterns shop!). An interesting thing about pattern testing clothing is seeing how differently a pattern can fit different body shapes. The same pattern might be tight for one lady in the same point where it is loose for another. Luckily, there are lots of ways to modify a pattern for a perfect fit, but today we’ll cover how to adjust the crotch in pants in the four most important and useful methods.

I’ll show you how to adjust the rise and the curve in the crotch, which can drastically influence how your garment fits and help make it flatter your body shape. Let’s get started!

Materials:

• A pants/trousers pattern (Here I am using the Simple Leggings for girls and the Evening Primrose Pajama Pants for women patterns, both available at the Cucicucicoo Patterns shop. I’ve printed them out on green paper simply so that they show up better in the photos.)
• Quilting ruler* (recommended, but if you don’t have one, a regular ruler will work, too)
• Pencil and scissors
• Invisible tape*
• Paper for expanding pattern (I use this medical paper for pattern drafting*.)

Lower/raise the front and back rise

This was an image showing the original low and high waist options for my Simple Leggings for Women pattern. Except it was definitely too high for both options, so I lowered it all around for the final pattern.

In this case we have to lower the rise of the pattern on both the front and back. The rise is the length of the curve between the crotch point and the top waist of the pattern. When the rise is too high, it pulls up too high on the waist and/or the fabric slips down both in the front crotch and the bum in the back, making unsightly sags.

You can make this adjustment on either a one-piece pants pattern, like my Simple Leggings, or a two-piece pants pattern, such as my Evening Primrose PJ pants. If you are making this adjustment on a two-piece pattern, make sure you modify both pieces in the same way or else the sides won’t align.

Draw a line across the pattern above the main crotch curve. To make sure it’s perfectly horizontal, I always line up a marking on the quilting ruler with the grainline arrow on the pattern.

Then cut straight across along the line.

You can pinch the fabric of your sewn pants while wearing them to see about how much you need to remove from the pattern. Then mark that amount below the cut on the lower pattern piece. For my example, I’m removing 1 cm, so I made a couple of marks 1 cm below the cut.

Then slide the top piece down so that the bottom edge hits the marks you’ve just made. Make sure that the grainline arrow or other markings in the center of the pattern are lined up, then tape the pattern in place.

There will be bits of the pattern edges sticking out, so just smooth out the curves by trimming it with your scissors (not shown).

Let’s say we have the opposite problem: the rise is too low in the front and the back. If this is the case, the garment’s waist will not reach all the way up to your body’s waist, so we need to add to the pattern.

I will continue to use the example of 1 cm. Start by cutting across the pattern as shown above. Then take the pattern-drafting paper and draw two parallel lines 1 cm apart (or the amount you need to raise the rise). Next, draw a perpendicular line going through both. (top image)

Match up the top line to the bottom edge of the top piece, matching the vertical line with the pattern’s grainline (or other perfectly vertical) marking, as shown by the arrow above, and tape it in place. Then match up the top edge of the bottom piece with the bottom line, again matching the vertical lines, and tape that in place.

Trim both layers of the pattern to make even curves, and you’re done! The bottom picture here has red paper underneath to better show the new curved edges.

Lower/raise the front OR the back rise

Now, let’s imagine that the back of your pants fits perfectly, but the front rise is too high. This was the case with my Birkin Flares. As you can see above, the jeans covered my bum and arrived perfectly to my waist in the back. On the front, however, the fabric sagged down terribly at the crotch. When I pulled them up higher, the fabric straightened out. This meant that the rise was too high ONLY in the front.

It is also possible for the rise to be too high or low only in the back, too. The adjustments to be made are the same.

To adjust the rise ONLY in the front or the back, you must have a pants pattern in two pieces. So here I am using my Evening Primrose PJ pants.

Lowering the rise

Draw a line across the front (or back) pattern piece as shown before. Remember to line up the ruler with the grainline arrow (shown by the arrow in the top picture). This is even more important with two-piece pants patterns because neither side is perfectly vertical.

Cut along this line, leaving only a tiny bit intact at the side so that the two parts can separate with the side as a hinge. Then mark the amount that needs to be removed (again, I’m doing 1 cm) below the cut along the crotch curve (shown by the arrow in the bottom picture).

Lower the top part so that the open edge hits the mark made below the cut (shown by the arrow in the top picture). Then tape the pieces together.

Trim off the pattern to smooth the curve out (shown by the arrow in the bottom picture).

Raising the rise

Now let’s imagine that the front fits perfectly, but your back waist is too low, putting you at risk for showing off your bum when you bend or move. In this case, we need to raise the back rise only.

Start in the same way as lowering the back or front rise. Draw a line across the back (or front) pattern piece as before. Remember to line up the ruler with the grainline arrow (shown by the arrow in the top picture). 

Cut along this line, leaving only a tiny bit intact at the side so that the two parts can separate with the side as a hinge (shown by the arrow in the bottom picture).

Put a piece of pattern drafting paper under the pattern and tape the edge of the bottom part to it. Then make a mark 1 cm (or the amount you need to raise it by) above the open side of this piece (shown by the arrow in the top picture).

Pull the top piece down so that the tip hits the mark (shown by the arrow in the bottom picture), and tape in place.

Trim the curve to even it out.

Remember that you can make both of these adjustments for either the front or the back of you pants. Here I’m showing how to lower the rise on the back only.

Adjusting the front crotch curve

When learning how to adjust the crotch in pants, a trickier adjustment to understand is the crotch curve itself. As a general rule of thumb, when the fabric folds up in big wrinkles because there is excess fabric, you need to make the pattern smaller, cutting off part of it along the curve. And vice versa, when the fabric stretches to fit around the body because there isn’t enough fabric, you need to add to the pattern at the curve.

Scooping out the front curve

In the example above, you can see that the waist fits where it should, so the rise doesn’t need to be adjusted. However there is a ridiculous amount of excess fabric wrinkling up at the crotch. You can pinch the fabric to get an idea of how much must be removed. 

Let’s say that we have to remove 1 cm on each side. Make a mark 1 cm in from the deepest part of the crotch curve (shown by the arrow). Then draw a new curve connecting the crotch point with the straighter part of the curve towards the top. Then cut along the line.

Making the front curve more shallow

Now let’s imagine the opposite scenario. When the front curve is too deep, the fabric pulls across the front, making horizontal lines, as shown in the image above from Bespoke Unit. This not only looks bad, but feels bad, too!

In this case, we have to do the opposite as before, and add to the pattern. Again, let’s imagine that we have to add 1 cm on each side.

Tape the crotch curve to a piece of paper below. I’m using another color simply to show up better in photos. Then make a mark on the extra paper 1 cm from the deepest part of the crotch curve (shown by the arrow). Then draw a new curve connecting the crotch point with the straighter part of the curve towards the top and cut along the line.

This adjustment adds fabric to the pants pieces, thus creating more space inside the garment.

Adjusting the back crotch curve

Adjusting the back crotch curve is basically the same as adjusting the front crotch curve. Likewise, the symptoms of this curve being too shallow or too deep are the same.

When the back crotch curve is too deep, the pants end up being too tight in the bum, creating horizontal lines as the fabric strains to reach across. And conversely, when the back crotch curve is too shallow, the pants are too wide across the bum, making the fabric sag. Both of these possibilities are shown in the image above, again from Bespoke Unit. 

Making the back curve more shallow

This is the adjustment that is more commonly used for the rear crotch curve, generally when the bum is proportionally larger than the rest of the bottom half of the body. In this case, we have to add to the pattern. Again, let’s imagine that we have to add 1 cm on each side.

Tape the crotch curve to a piece of paper below. Then make a mark on the extra paper 1 cm from the deepest part of the crotch curve (shown by the arrow). Then draw a new curve connecting the crotch point with the straighter part of the curve towards the top and cut along the line.

This adjustment adds fabric to the pants pieces, creating more space around the bum.

Scooping out the back curve

When there is excess fabric sagging around the bum, you can pinch it to get an idea of how much must be removed. As usual, let’s say that we have to remove 1 cm on each side.

Make a mark 1 cm in from the deepest part of the crotch curve (shown by the arrow). Then draw a new curve connecting the crotch point with the straighter part of the curve towards the top. Then cut along the line.

There are many other ways to adjust pants patterns, but these are most common and useful techniques to know when learning how to adjust the crotch in pants. Understanding how to analyze the fit of your trousers and what modifications to make in the pattern will allow you to create the perfect fit that will flatter your unique body!

Another important adjustment that you can make to a pants sewing pattern is lenthening or shortening the legs. This is particularly useful if you are taller or shorter than average. Learn how to adjust the length of legs here!

If you want to get started sewing your own leggings, pants or trousers, make sure you check out the patterns in the Cucicucicoo Patterns shop!

Also, make sure you sign up for the Cucicucicoo Newsletter here for access to tons of free creative templates, patterns and downloadables! The Newsletter is sent out every other week with lots of great ideas and links to a different free sewing pattern every week!

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