Same height. Different bike.
A size chart maps one number, your height, to a frame. But two riders of the same height can have legs 8 cm apart. That moves their saddle height by about 70 mm and changes how far they can reach.
Sizes aren’t standard either: one brand’s M can sit closer to another’s L. The calculator looks at your body and the exact bike instead.
The chart, and where it breaks.
This is the standard road and gravel chart. Read it by height and both riders from above get the same answer. Read it by inseam and they land two rows apart.
Road & gravel · frame measured centre to top of seat tube
- 150–160 cmXSInseam 70–75 cmFrame 47–50 cm
- 160–170 cmSInseam 75–80 cmFrame 50–53 cm
- 170–179 cmMInseam 80–84 cmFrame 53–56 cmRider B · inseam 82
- 179–189 cm← your heightLInseam 84–89 cmFrame 56–59 cmBoth riders · 182 cm
- 189–198 cmXLInseam 89–93 cmFrame 59–62 cmRider A · inseam 90
Gravel frames from some brands run about one size smaller. MTB XC frames are sized by reach, not seat tube. The letters don’t transfer, so use the calculator.
A book, a wall, one minute.
Your cycling inseam is not your trouser length. The calculator repeats these steps next to each field.
- 1Stand barefoot against a wall with your feet 10–15 cm apart.
- 2Press a hardback book up between your legs like a saddle, level against the wall.
- 3Measure from the floor to the top edge of the book. Repeat and use the value you get most often.
Measure twice: your saddle height is calculated from this number.
Why the frame letter is not enough.
What decides fit is stack and reach: how high and how far forward the handlebars sit from the pedals. The calculator compares the stack and reach of every size of your bike with the position your body needs, then picks the size and the parts that close the gap.
The number that matters most.
Saddle height comes from your legs, not from the frame. The calculator places your leg on the pedal at the bottom of the stroke and checks the knee angle against its target window.
A shop sets a new bike up for the average rider of that size. If you are not average, that is where knee pain starts.
See yourself on the bike before you buy it.
- Your size on any model, every size compared. Free.
- Your saddle height for the size you pick. Free.
- Setback, stem, spacers, bars, cranks and your knee, back and elbow angles: one payment, one-time per bike.