Bicycle Frame Size Guide
Find your bike frame size by height and inseam. Different rules for road bikes, mountain bikes, hybrids, gravel.
How bike sizes are labeled
Road / gravel bikes
Sized in cm based on seat tube length: 48, 50, 52, 54, 56, 58, 60, 62 cm. Or by letter (XS/S/M/L/XL). Frame "stack and reach" matter as much as seat tube.
Mountain bikes
Sized in inches (15", 17", 19", 21") or letters (S/M/L/XL). Newer geometry trends to "long, low, slack" — modern MTBs run roomier than 5 years ago.
Hybrid / commuter bikes
Usually letters (S/M/L) or cm based on seat tube. Less precision needed since upright posture is forgiving.
Kids bikes
Sized by WHEEL diameter, not frame: 12", 14", 16", 18", 20", 24", 26". Match wheel size to child's inseam (their leg should reach the ground when seated).
FAQ
Between sizes — up or down?
Road: down for racy/aero fit, up for endurance/touring. MTB: up for newer geometry (more reach). Hybrid: down for nimbleness.
What if I have a long torso or long legs?
Standard charts assume average proportions. Long torso + short legs: size up (fits torso). Long legs + short torso: size down with a longer seatpost (raises seat without making reach too far).
Do women's bikes fit differently?
Women-specific bikes have shorter top tubes + shorter reach for shorter average torsos. But many women fit unisex bikes fine — just adjust stem length + saddle setback. Trek's WSD line and Liv (Giant women's brand) are the gold standard if you want women-specific.
How important is professional bike fitting?
For a bike under $500: not very. For $500–$2000: helpful (saves you from a wrong-size purchase). $2000+: get fitted at a shop BEFORE buying. Pro bike fit costs $150–$300 and saves your knees over the long term.