What size bike frame do I need?
Start from height, confirm with inseam. The chart below is the consolidated version of the published sizing charts — and notice the bands overlap on purpose: two riders of identical height regularly belong on different frames, because frames are bought with torsos as much as legs. That overlap zone is where this calculator does its real work.
| Height | Road / gravel | Mountain |
|---|---|---|
| 4′10″–5′2″ (147–157 cm) | 47–49 cm · XXS | 13–14″ · XS |
| 5′1″–5′5″ (155–165 cm) | 49–52 cm · XS | 15–16″ · S |
| 5′4″–5′8″ (163–172 cm) | 52–54 cm · S | 17–18″ · M |
| 5′7″–5′10″ (170–178 cm) | 54–56 cm · M | 17–18″ · M |
| 5′9″–6′0″ (176–184 cm) | 56–58 cm · L | 19–20″ · L |
| 6′0″–6′3″ (182–190 cm) | 58–60 cm · XL | 21–22″ · XL |
| 6′2″–6′7″ (188–200 cm) | 60–63 cm · XXL | 23″+ · XXL |
Rendered from the same data the calculator uses. Gravel bikes size like road; hybrids too, a touch relaxed. Every brand's geometry differs — treat the letter as a shortlist, not a verdict.
Between sizes: the answer the shop calculator won't give you
Most sizing tools shrug — "either could work!" — which is true and useless. The real tiebreaker is your proportions. Frames grow in length as much as height: the taller size mainly buys a longer top tube. So if your legs are long for your height (inseam ÷ height above ~0.47), the smaller frame fits your shorter torso and the seatpost makes up the leg room — size down. Legs short for your height? The bigger frame's length suits your longer torso — size up. Then the second-order honesty: flexibility. Riders who want a relaxed back choose the size (and stem) that brings the bars closer and higher. This calculator runs the proportion math for you; the flexibility call is yours.
The classic formula multiplies inseam by 0.665 for road (0.575 MTB, 0.645 hybrid): an 84 cm inseam suggests a ~55.9 cm road frame. It's a useful cross-check on the height chart — when the two disagree, you're a between-sizes rider and the proportions logic above is the tiebreaker, not a coin flip.
One brand's 54 is another's 56 is a third's "M" — seat tubes are measured to different points and sloped differently, so the label on the frame drifted into vanity sizing years ago. The numbers that actually describe a frame are stack and reach (vertical and horizontal distance from bottom bracket to head tube), printed in every geometry chart. When you shortlist two bikes, our stack & reach calculator compares them properly — including the spacer-and- stem translation to match your current position.
Does this replace a bike fit?
No — and any calculator that implies otherwise is selling something. Sizing gets you on the right frame; fit is what happens on top of it — saddle height and setback, bar reach and drop, cleats. Get the frame size right first (wrong frames can't be fitted out of being wrong), start with our saddle height calculator once the bike is in the stand, and if you're riding serious miles or hurting, a professional fit is the best money-per-comfort in cycling.
Sizing a used or older bike
Older road frames were measured center-to-top of longer seat tubes, so a vintage "56" often fits like a modern 54 — another reason to trust standover and top-tube feel over the decal. Quick used-bike checks: standing over the top tube flat-footed you want clearance (a couple of centimeters road, more for mountain); and with the saddle at your height (the calculator gives the number), at least a few centimeters of seatpost should remain in the frame. Post at its limit means the frame is too small, however right the sticker sounds.