Bike Frame Size Calculator

Turn your height and inseam into a frame size for road, mountain, hybrid and city bikes, plus saddle height, standover clearance, crank and stem length.

Frame size is set by leg length, not by height alone. Two riders of the same height can need frames 2 cm apart. Enter your inseam and height, pick the bike type, and the page returns a starting frame size, saddle height and the contact-point measurements you can set up at home.

Your measurements

Measure inseam barefoot, feet 20 cm apart, from the floor to the crotch — the same way a tailor measures a trouser inseam. Use a book pulled up firmly against the wall.

Height (cm) Inseam (cm) Bike type

Frame size –

Saddle height –

Max standover –

Crank length –

Stem length –

Wheel size –

How this was worked out

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Frame size by height, as a cross-check

Height	Road	Mountain	City / hybrid
155–160 cm	48–50 cm	14–15 in	S
160–165 cm	50–52 cm	15–16 in	S
165–170 cm	52–54 cm	16–17 in	M
170–175 cm	54–55 cm	17–18 in	M
175–180 cm	55–57 cm	18–19 in	M–L
180–185 cm	57–58 cm	19–20 in	L
185–190 cm	58–60 cm	20–21 in	L–XL
190–195 cm	60–62 cm	21–22 in	XL

Four rules before you buy

Frame size is a starting point, not a verdict. Reach and stack differ between brands, so compare the effective top tube of the bike you are looking at with the frame you ride now.
A frame that is too big is worse than one that is too small. You can lengthen a stem and raise a seatpost; you cannot shorten a top tube.
Saddle height is measured from the centre of the bottom bracket to the top of the saddle, along the seat tube — not from the ground.
Standover is a hard limit for mountain bikes. You need 5–10 cm of clearance above the top tube when standing flat-footed over the bike.

Practical notes

Set saddle height first, then saddle fore-aft, then stem and bar height. Changing the order makes every adjustment fight the last one.
Crank length is shifting: riders under about 165 cm often ride better on 165 mm cranks, and very tall riders on 175 mm.
For a child, size by standover and reach, not by wheel size. A 24-inch wheel bike can fit a 130 cm rider or a 150 cm rider depending on the frame.

Three common mistakes

Choosing by height alone. Height tables assume average proportions; a rider with long legs and a short torso needs the smaller frame with a longer stem.
Measuring inseam in shoes. Shoes add 2–3 cm and push you up a frame size. Measure barefoot.
Setting saddle height by "heel on the pedal". That method only works with the correct shoe and cleat; the 0.883 × inseam figure is repeatable.