Mountain-bike sizing is not determined by one measurement. Frame size charts help narrow the range, but reach, stack, standover, saddle position, cockpit length, riding style, and your body proportions all affect fit.
Start with the manufacturer’s size chart
Use your height and inseam as a starting point, then compare the geometry of nearby sizes. Different brands can label similar bikes differently, so “medium” is not a universal measurement.
Reach and stack matter
Reach describes the horizontal distance from the bottom bracket area to the top of the head tube and strongly influences how long the bike feels while standing. Stack describes vertical height and affects front-end position. Together they are more useful than old rules about saddle-to-handlebar height.
Standover is a clearance check, not the whole fit
You should have adequate clearance to stand over the bike safely, but fixed rules such as “four to six inches” do not apply to every frame design. Modern sloping top tubes can create substantial clearance even when the bike’s reach is long.
Set saddle height for pedaling first
For general riding, saddle height should allow efficient pedaling without excessive hip rocking or overextension. A dropper post can then lower the saddle for descending and technical terrain rather than forcing the normal pedaling position to be artificially low.
Handlebar height is personal
There is no rule that the handlebar must sit below the saddle. Bar height and stem length depend on frame geometry, flexibility, terrain, riding style, and comfort.
Between two sizes?
A smaller size may feel more compact and maneuverable; a larger size may feel roomier and more stable. Geometry changes across sizes, so compare actual measurements rather than choosing based only on height.
Test ride whenever possible
Check whether you can comfortably reach the controls, move around the bike, pedal without joint strain, and feel balanced while standing. If pain, numbness, or persistent discomfort appears, adjust the setup or seek professional bike-fit advice.
