Start with inseam
Multiply your inseam by 0.66 for an indicative frame size in centimetres. An 82 cm inseam gives about 54 cm. This number is a starting point: a brand may label the same candidate frame 53, 54, M or even S.
Size labels are not standardised
| Label | What it may describe | What to compare |
|---|---|---|
| 48–62 cm | Nominal seat-tube size | Stack and reach |
| XS–XXL | Brand-specific range | Exact geometry chart |
| Race / endurance | Intended position | Handlebar height and cockpit length |
The dimensions that matter
Reach and effective top tube
Reach describes how long the frame feels. Effective top tube also helps compare familiar bikes, but the stem and handlebar reach influence the final hand position.
Stack
A higher stack makes an upright endurance position easier. A low race frame asks for more mobility and may remain aggressive even with spacers.
Standover
Keep comfortable clearance above the top tube when standing over the bike, especially if the frame has a nearly horizontal tube.
Between two sizes
The smaller candidate usually feels more compact and agile and can be lengthened slightly with normal cockpit adjustments. The larger candidate may feel more stable, but it cannot always be shortened without compromising handling.
Before ordering
- Measure height and inseam twice.
- Compare stack and reach with a bike you know.
- Check the supplied stem, handlebar and crank length.
- Confirm adjustment limits for the fork steerer and seatpost.
- Test ride whenever possible.