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About this tool
Set bike saddle height and setback from your inseam using the LeMond 0.883 and Hamley 109% fit methods, with crank length guidance.
Saddle height is the single setting that most affects comfort and power on a bicycle, and two published methods pin it down from one measurement. The LeMond method places the saddle top at 0.883 × cycling inseam above the bottom-bracket centre; Hamley and Thomas (1967) found peak efficiency at 109% of inseam measured from the pedal spindle at bottom dead centre, which is the same thing minus crank length. This calculator runs both, shows the working window fitters use (0.875-0.892 × inseam), converts the figure to a saddle-to-pedal measurement, and adds setback and crank-length guidance for your riding position.
Open Saddle Height Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
LeMond and Hamley agree within millimetres when both are computed correctly.
Shows the acceptable range so small differences do not read as errors.
Position-specific setback ranges and a 20-21% inseam crank guide.
Multiply your cycling inseam in centimetres by 0.883 to get the distance from the bottom-bracket centre to the saddle top: an 83 cm inseam gives about 733 mm. Anything between 0.875 and 0.892 × inseam is a reasonable working window, and small riders should measure rather than scale from a chart.
A saddle that is too high makes your hips rock side to side, over-extends the hamstrings and causes pain behind the knee or in the Achilles. Too low overloads the quadriceps and typically causes pain at the front of the knee. The target is 25-35 degrees of knee flexion with the pedal at bottom dead centre.
Yes — move the saddle by the same amount in the opposite direction. Fitting 170 mm cranks in place of 172.5 mm shortens the reach to the pedal at bottom dead centre by 2.5 mm, so raising the saddle 2.5 mm restores identical leg extension.
Roughly 5-9 cm for an endurance road position, 4-7 cm for a race position, 3-7 cm on a mountain bike and 6-10 cm on an upright city bike; time-trial positions run from 3 cm behind to 3 cm ahead. Confirm on the bike with a plumb line from the bony bump below the kneecap with the cranks horizontal.
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