Bike Gear Ratio Calculator

Gear ratios, cadence and speedRuns locally · nothing uploaded

Chainrings (comma separated)Common cassettesCassette cogs (comma separated)Tire sizeWheel circumference (mm)Cadence (rpm)

Show in table

⚙	11	12	13	14	15	17	19	21	23	25	28
50
34

Tap a cell for details. Darker cells are harder gears.

Selected gear

50 × 17

Speed at 90 rpm

33.4 km/h

Ratio

2.94

Development (m) · Gear inches

6.19 m · 77.6″

Target speed (km/h)

Cadence needed for target speed

81 rpm

Also works as:gear ratio calculatorbike gear calculatorcadence to speedgear incheschainring cassette

How it works

Ratio = chainring ÷ cog

Speed (km/h) = ratio × circumference (m) × cadence × 60 ÷ 1000

Gear inches = ratio × wheel diameter (in)

Given: 50 × 17 on 700×25C (2105 mm) at 90 rpm

Result: About 33.4 km/h (77.6 gear inches).

1Enter chainrings (e.g. 50,34) and choose or type cassette cogs.
2Pick a tire size or enter the circumference (mm), and set your cadence.
3Read the gear table and tap a cell for details; use the target speed box for cadence.

How is gear ratio calculated?

Ratio = chainring teeth ÷ cog teeth. Speed (km/h) = ratio × circumference (m) × cadence × 60 ÷ 1000. 50×17 on 700×25C at 90 rpm is about 33.4 km/h.

What cadence should I ride?

Many road riders are efficient around 80–95 rpm. Grinding big gears at low cadence loads the knees—shift easier and spin faster.

How do I measure wheel circumference?

Mark the tire, roll one full revolution and measure the distance, or use your bike computer's tire table. Pressure and load change it slightly.