Gear Ratio Calculator — Speed for Every Gear

Which gear makes you how fast? The calculator below shows your speed for every chainring-and-cog combination at a given cadence — sorted from the easiest to the hardest gear. Pick a complete groupset, or set chainrings, cassette, cadence and tire size freely.

Instead of a dry table you get a bar chart: each bar is a gear, its height the speed. Tap a bar to see it as a drivetrain below.

Gear ratio, development and speed — what’s behind it?

The gear ratio is the number of chainring teeth (front) divided by cog teeth (rear). 50 up front and 25 in the rear give a ratio of 2.0: one crank revolution turns your rear wheel twice.

Development (or rollout) is how many meters you travel per crank revolution — ratio times wheel circumference. That is exactly why the calculator needs your tire size: a bigger tire rolls farther per revolution, so you go slightly faster in the same gear.

1x or 2x — which gearing suits you

A 2x drivetrain (two chainrings) gives fine steps and a wide overall range — ideal for road and hilly routes. A 1x drivetrain is simpler, lighter and lower-maintenance: one chainring, but a wider cassette. It is now standard on gravel (SRAM XPLR, Shimano GRX) and MTB (SRAM Eagle, Shimano XT). What matters is not the number of chainrings, but the largest ratio you can reach.

Wheel circumference — where the values come from

The tire presets use the standard circumference table that bike computers from Garmin, Wahoo or Sigma also use — sorted by tire size (700×28C, 27.5″, 29″ …), not by model. Between two tires of the same width the circumference differs by only a few millimeters, negligible for speed. If you want it exact, measure your roll-out circumference once and enter it in the wheel circumference field.