Manufacturer height charts are a reasonable starting point for mountain bike sizing, but they're not the whole story — two riders of the same height can end up wanting different frame sizes depending on proportions and riding style.
Start with the height chart, but don't stop there
Most brands publish a recommended height range per frame size, and it's a fine first filter. Where it falls short is inseam length and torso-to-leg ratio, which vary between riders of the same overall height and affect standover clearance and reach more than height alone does.
Standover height
Standover height is the clearance between the top tube and your body when you're straddling the bike with both feet flat on the ground. On a mountain bike you want real clearance here — a few inches at minimum — since you'll be putting a foot down quickly on technical terrain, unlike on a road bike where standover matters less.
Reach and riding style
Reach — roughly the horizontal distance from the bottom bracket to the head tube — has a bigger effect on how a bike feels than most riders expect. A shorter reach feels more upright and maneuverable at low speed; a longer reach feels more stable at speed on descents. Riders who prioritize technical, slower-speed trails sometimes size down from the chart's suggestion; riders focused on descending speed sometimes size up.
When in doubt
If you're between two sizes on the chart, your riding style and local terrain are usually the tiebreaker rather than a universal rule. Browse frame specs across sizes in our Mountain & Trail Bikes collection.