Bike Size Calculator

How to Find Your Bike Frame Size

The right frame size improves comfort, power, and control. This calculator uses your inseam (inside leg length) to estimate frame size for road, mountain, and trekking bikes, plus wheel size for children.

Frame Size Formulas

Road bike: frame size = inseam (cm) × 0.67
Trekking / city bike: frame size = inseam (cm) × 0.64
Mountain bike: frame size = road frame size − 11 cm

Mountain frames run smaller because riders need more clearance and a more upright, agile position on rough terrain.

Measuring Your Inseam

Stand with your back to a wall, feet 15 to 20 cm apart. Place a book between your legs like a saddle and mark where the spine meets the wall. Measure from that mark to the floor. Accurate inseam measurement matters more than height alone because leg length varies between riders of the same height.

Frequently Asked Questions

What bike size do I need if I am 183 cm tall?

With an inseam around 81 cm, expect roughly 54 cm for a road frame, 52 cm for trekking, and 43 cm for mountain. Always confirm with the manufacturer's size chart.

Why is inseam more important than height?

Frame size is tied to leg length, which determines standover height and reach. Two riders of the same height can need different frames if inseam differs.

How are kids bike sizes measured?

Children's bikes are sized by wheel diameter (12, 16, 20, 24 inches, and so on), not frame centimeters. Match wheel size to inseam so the child can straddle the bike safely.

Are frame sizes the same across brands?

No. Manufacturers measure differently and use unique geometry. Treat these results as a starting range and check each brand's chart before buying online.

Should I get a professional bike fit?

A professional fit is the most accurate option. This calculator gives a useful estimate when you cannot test ride, especially for online purchases.

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How to Find Your Bike Frame Size

Frame Size Formulas

Measuring Your Inseam

Frequently Asked Questions

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