After the first Sewing with Denim post, many readers brought up concerns in sewing pants for themselves or their children. Many also made comments that pants patterns seem intimidating and measurements all over the board mean size mashing is needed. Don’t worry, friends! I’ve got you!!! In this blog post we’ll talk about the anatomy of a pant (I don’t know if that’s a thing but I’m calling it that!), how to reference a size chart and how to modify a pants pattern for the perfect fit. This post is meant to be easy for a beginner to read and put into practice, but at the end of the post I’ll be linking up other great resources for more in-depth alterations that may be needed! Let’s get to it!
The Anatomy of the Pant Pattern
Let’s take a look at the key part of the pant pattern that you will want to pay close attention to when mashing sizes or altering a pattern for a better fit. For example sake, I’ve created a general pattern piece for a pant front and back, please note that it is not intended for real use.
Side Seam: This is the part of the pant that is on the outside of the legs from the waist to the hem, where the front and the back pant pieces are joined.
Inseam: This is the part of the pant that runs along the inside of the legs, from the crotch to the hem.
Front rise: This is the curve of the pant that runs along the front from the waist to the crotch.
Back rise: This is the curve of the pant that runs along the front from the waist to the crotch. Usually the back rise is longer than the front to accommodate the bum!
Measuring for a Better Fit
Taking accurate measurements and using those measurements to reference a size chart is critical in sewing a great fitting garment. There are a few key measurements needed in order to help choose the correct size(s) to use when cutting out your pants pattern.
Waist: Measure around the wearer where the top of the pant will sit. Keep in mind that usually a waistband is added, so measure lower for the top of the pant versus the top of the waistband.
Hip: Measure around the wearer at the fullest part of the hip. The hip measurement is usually take between the waist and the crotch.
Thigh: Measure around the fullest part of the wearer’s leg.
Knee: Measure around the wearer’s knee.
Inseam: Measure from the crotch to where you’d like the hem to hit along the inside of the wearer’s leg.
Leg opening: Measure around the wearer’s ankle, allowing for ease to fit the foot through the leg opening.
After taking these measurements, reference the size chart for the pants pattern you’d like to use. Keep in mind size charts vary by designer so just because the wearer needs a size 4 for one company doesn’t mean they will need a size 4 for another.
When referencing the size chart, find where the wearer’s measurements fall for each of the key points mentioned above. Specifics such as the knee and leg opening may not be included. You can use those measurements and the size chart to mash sizes for each of those key points if needed.
Mashing for a Better Fit
Since most people don’t fit the same standard size according to a size chart for their waist, hip, thigh and inseam, mashing multiple sizes is needed for a great fitting garment. Let’s look at a specific example and some tips for mashing multiple sizes. Note: This technique works best when mashing among 2-3 sizes. If further mashing is needed, a muslin is suggested with custom alterations for the most perfect fit. 
In this specific example, let’s say size 4 is blue, size 5 is green and size 6 is yellow. The black lines drawn in is the new custom pattern piece. Note that the sizes are nested with the crotch points aligned. This will make for easy mashing. If you have a pants pattern where that point is not aligned, you may want to cut out each size, align them at the crotch point and tape them together before starting to mash.
If the wearer has a size 4 waist, size 5 hip and thigh and a size 6 length, mashing will help you sew pants that will fit the wearer nicely.
Start by marking the length. You’ll want to keep the rise, the inseam and the side seam a size 6 (for this example). If you alter the rise, inseam or side seam to be any shorter than the needed length, you will end up with pants that are too short or sit too low on the wearer. If your wearer needs a shorter length than their width size, draw horizontal lines across the pattern pieces at the size for the length.
Next, mark the waist. You’ll simply extend the size 4 waist line up to the size 6 for this example.
Then, mark the hip, thigh and leg opening. You’ll draw a curve from the waist markings out to the size 5 hip, thigh and down the pant leg. You follow the same process along the rise and inseam of the pant.
Note any of these alterations will need to be transferred to other pattern pieces such as the waistband, hem facing, pockets, etc.
Once you’ve customized the pattern piece at the waist, hip, thigh, etc. you’ll cut the pattern pieces out along those new lines and get to sewing!
I hope you found some helpful tips and tricks in this post. Sometimes even further alterations are needed but get to be a bit more complicated and are geared towards the advanced sewist. Some helpful links for problem areas are included below.
A great video on altering the crotch length.
A full thigh alteration plus other great tips.
A Craftsy class for altering pants.
For more precise altering for jeans (this is geared towards ladies’ wear)
How to alter for cloth diapers.
Cassie Nicole Creates 