Inseam at a glance
- Measured from
- Crotch seam to hem, inside the leg
- Trail default
- 5 inches
- Long-run choice
- 7 inches
- Changes with
- Garment size, and whether the hem is split
What the number controls
Inseam sets a trade between stride freedom and coverage. A short inseam gets fabric out of the way of a high knee and vents heat, which is why mountain racers wear them.
A long one protects the inner thigh from brush, sun and a slide onto scree, and gives a liner enough room to sit where it was drafted to sit. Neither end is correct; they suit different runs and different bodies.
The usual lengths
Three inches is a racing length, largely borrowed from road running, and leaves a lot of leg exposed.
Five inches is the modern default and what most trail-specific shorts are cut to: enough coverage for most terrain without catching a high step.
Seven inches is where people running long tend to settle, because it covers the inner thigh properly and stops the hem riding up on a steep climb.
Nine inches and above starts behaving like a hiking short, which suits a hike-run pace but adds fabric that flaps on a fast descent.
Why the number alone is misleading
A split hem or a side vent lets the leg opening flare as the knee comes through, so a seven-inch short with a split can move like a five-inch one without a split.
Measured inseam also shifts with size, since most makers grade the leg length up and down along with the waist, so the same nominal number is a slightly different garment at each size.
What this means when you're choosing
- Whether the maker states inseam for your size or only for a sample size
- A split hem or side vent, which makes a longer inseam move like a shorter one
- Where the hem lands relative to the widest part of your thigh
- Whether the liner inseam is quoted separately from the shell inseam
The common mistake
Sizing down in inseam as runs get longer
Shorter shorts feel faster and expose more inner thigh, which is the exact area that rubs over hours. If you are between lengths and your distances are creeping up, take the longer one.
Common questions
How do I measure my inseam?
Measure a pair of shorts that already fit rather than your leg. Lay them flat and measure the inner seam from the crotch join to the hem. Doing it on your body needs a second person and still tends to read long.
Is inseam measured differently for women's shorts?
It is measured the same way, but the conventional range sits shorter. Women's trail shorts are commonly offered from about two and a half inches to seven, so the same number reads differently between the two ranges.