How to measure inseam
The inseam is the distance from the crotch seam straight down the inside leg to the bottom hem. Measure it on a pair of trousers laid flat, in inches, with the seams smoothed straight.
Last verified: 26 August 2026
Two things get called the inseam, and confusing them is where most trouser sizing goes wrong. On a garment, the inseam is the seam running from the crotch point straight down the inside of the leg to the bottom hem. On a body, it is the distance from the crotch to the floor. The number printed on a label is the garment one, and it is the one you can check yourself with a tape measure in about two minutes.
What is the inseam?
The inseam is a single straight measurement along the inside leg. It starts where the two leg seams meet at the crotch and ends at the bottom edge of the hem. It is taken with the garment flat, one leg smoothed out, and the tape held straight rather than following the drape of the fabric.
It is a length, not a circumference. Nothing about the inseam tells you how wide the leg is or how much room there is through the thigh. It answers one question: how far down your leg the trouser ends.
Taken on a garment it is repeatable. Two people measuring the same pair laid flat will usually land on the same figure; two people measuring the same body will not. That is why the garment method is the one to prefer whenever you own a pair you already like.
How do you measure the inseam on trousers you already own?
This is the preferred method because it is repeatable and needs nobody's help. Use a pair whose length you are happy with, not the pair you are trying to replace because it is wrong.
- Wash and dry them first, if you can — cotton denim and cotton twill shrink most in their first few washes, and measuring a brand new unwashed pair records a length the garment will not keep.
- Lay them flat and face down on a hard surface — a table or a floor, never a bed. A soft surface lets the fabric sink and adds length you cannot see.
- Button and zip the fly — an open fly lets the front rise spread and pulls the crotch point out of position.
- Fold one leg back over the other — bring the top leg out of the way so the inside seam of the bottom leg lies exposed and straight along the surface.
- Smooth the leg straight down, without stretching it — press wrinkles out with a flat hand. Pulling the fabric taut adds length; leaving a ripple in it hides length.
- Find the crotch point — the spot where the front rise seam, the back rise seam and both inside leg seams converge. That intersection is the start of the measurement, not the fly, not the waistband.
- Run the tape straight to the bottom hem — hold the end at the crotch point and take it down the inside seam to the very bottom edge of the finished hem, not to the top of the hem stitching.
- Read it in inches and write it down — record the number to the nearest quarter inch, then measure the other leg the same way. A quarter inch difference between legs is ordinary; anything larger usually means one leg was not smoothed flat.
If the trousers are cuffed, unfold the cuff before you measure and record the unfolded length. A cuff is a styling choice made after the length is set, and folding it in makes your figure impossible for anyone else to reproduce.
How do you measure a leg inseam?
Measure the body only when you have no trousers that fit to copy from. It needs a second person, and it carries more error than the garment method because the crotch point on a body is a judgement rather than a seam.
- Stand barefoot against a wall — heels, back and shoulders touching, feet roughly hip width apart, weight even on both feet. Shoes add anything from a quarter inch to well over an inch.
- Wear thin, fitted clothing — loose trousers make the helper guess where the crotch actually is.
- Have the helper hold a hardback book spine-up between your legs — pulled up firmly against the crotch until it stops, kept level. The spine gives a flat, repeatable top point in place of a soft one.
- Mark the wall at the top of the book's spine — a pencil line or a strip of tape, level with the spine, not angled.
- Step away and measure from the mark to the floor — hold the tape flat against the wall, straight down. That distance is your leg inseam.
- Repeat it once — take the whole measurement a second time from scratch. If the two readings differ by more than half an inch, take a third and use the middle value.
A leg inseam is not a trouser inseam. It tells you where the floor is, and you then subtract for the break you want: a shorter finished length for a clean no-break hem, a longer one for fabric that stacks on the shoe. How much to subtract depends on the shoe, the leg opening and your own preference, which is why copying a garment you already like beats calculating from the body.
What is the difference between inseam and outseam?
The outseam runs down the outside of the leg from the top of the waistband to the same bottom hem. It is always the longer of the two, and the gap between them is the rise. Some brands, particularly in workwear and in European sizing, publish outseam rather than inseam, so check which one a chart means before comparing it to your own number.
| Measurement | Starts at | Ends at | Taken on |
|---|---|---|---|
| Inseam | Crotch point | Bottom hem edge | Garment, laid flat |
| Outseam | Top of waistband | Bottom hem edge | Garment, laid flat |
| Front rise | Crotch point | Top of front waistband | Garment, laid flat |
| Back rise | Crotch point | Top of back waistband | Garment, laid flat |
| Leg inseam | Crotch | Floor | Body, standing barefoot |
How does rise change the inseam you need?
Rise and inseam share an endpoint, so they trade against each other on the same body. A higher rise sits the crotch point higher up you, which means a given inseam finishes further down your leg. Drop to a lower rise and the same inseam finishes shorter, because the whole garment has started lower.
The practical consequence: an inseam copied from one pair only transfers cleanly to another pair with a comparable rise. Moving from a mid rise to a high rise cut, expect the same printed inseam to break lower on the shoe. Measure the front rise on both pairs and treat the difference as a rough adjustment to the length you are looking for.
What goes wrong most often?
Two habits are worth breaking as well: measuring the trousers while wearing them, which moves the waistband and therefore the crotch point, and trusting a single reading. Stretch fabrics need their own caution, because any blend with elastane reads longer under tension. Let the leg rest at its natural length and keep the tape against it rather than pulled tight.
Does a labelled inseam mean the same thing at every brand?
Less reliably than you would hope. Inseam is at least a physical dimension rather than a letter, which puts it well ahead of a Medium or a Large for precision. But the printed figure is a target, and finished garments vary around it within the manufacturer's tolerance, which on published specs generally runs somewhere between plus or minus 0.3 and 0.8 inches.
The drift is worse on letter and waist-only sizing, where the same word covers different garments across cuts. Our page on vanity sizing works through what the published specifications actually show on tops. The lesson carries straight over to trousers: compare measurements, not labels.
What standard does ShirtMath measure to?
One standard, applied everywhere on this site: flat, in inches, seams smoothed, garment unstretched, tape held straight. Every measurement is taken on the garment rather than the body, and the figure recorded is the finished dimension, not a design target.
What is live today is shirt measurement. Photograph a shirt laid flat with a scale card and ShirtMath reads its flat measurements, then matches them against published garment measurements across the catalogue. Roughly half of those scanner readings land within an inch of a tape measure; sleeve opening and bicep are the least reliable points, and anything the scanner cannot read confidently is left blank rather than guessed. Trousers are not part of the photograph flow, so for an inseam the tape measure and the steps above remain the method.
Definitions for every point of measure are collected in the glossary, and the full measuring protocol is set out on the methodology page.
Where should you go next?
On its own the inseam will not tell you whether a pair fits. Take the waist, the front rise and the leg opening at the same sitting and you have a profile you can compare against any chart.
Where exactly does the inseam start?
Should I measure the inseam before or after washing?
Is the inseam the same as the outseam?
Can I measure my inseam without a second person?
Why does the same inseam fit differently in different trousers?
Trousers still need a tape measure, but shirts do not. Photograph a shirt laid flat with a scale card and ShirtMath reads its measurements, then finds garments whose published numbers match.
Scan a shirt