Loading page
About this tool
Find your road, mountain or hybrid bike frame size from height and inseam using the classic inseam-multiplier fit formulas.
Bicycle frame size is set by your inseam, not your height, and this calculator applies the classic fit multipliers to prove it: road seat tube = inseam × 0.67 centre-to-top (0.65 centre-to-centre), mountain frame in inches = inseam in centimetres × 0.226, and hybrid = inseam × 0.63. It reports those alongside the height-band chart a bike shop quotes, plus the LeMond saddle height of inseam × 0.883 and the standover clearance each discipline needs. Two riders of the same height can need different frames, and seeing both methods side by side shows when that is happening to you.
Open Bicycle Frame Size 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.
The measurement that actually determines standover and saddle height drives the answer.
Formula result and shop height chart appear together so disagreements are visible.
The LeMond figure gives you a starting seatpost setting on day one.
As a starting point, a 175-183 cm rider takes a 56-57 cm road frame, a 19-20 inch mountain frame or a 51-53 cm hybrid. Confirm with inseam: multiply your cycling inseam in centimetres by 0.67 for a road seat tube, so an 83 cm inseam gives about 55.6 cm.
Stand barefoot with your back against a wall, feet about 15 cm apart, and pull a hardback book firmly up between your legs to mimic saddle pressure. Measure from the floor to the top edge of the book — for most adults this comes to 44-48% of standing height.
About 2.5-5 cm between your inseam and the top tube for a road or hybrid bike, and 5-10 cm for a mountain bike because you dismount onto uneven ground. If the frame's standover height exceeds your inseam you cannot stand over it safely and the frame is too big.
The LeMond method sets bottom-bracket centre to saddle top at inseam × 0.883 — an 83 cm inseam gives roughly 73.3 cm. Set that, ride it, then adjust in 2-3 mm steps: pain at the front of the knee usually means the saddle is too low, pain behind the knee or rocking hips means too high.
Add the Bicycle Frame Size Calculatorwidget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/bicycle-frame-size-calculator"
title="Bicycle Frame Size Calculator — free AltFTool widget"
width="100%" height="640" style="border:0;border-radius:12px;overflow:hidden"
loading="lazy" referrerpolicy="no-referrer-when-downgrade"></iframe>
<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/tools/all/bicycle-frame-size-calculator?utm_source=embed&utm_medium=widget">AltFTool — free online tools</a></p>