Gear Speed Calculator
Pick a chainring, a cog, your wheel size and a cadence — this calculator turns them into road speed, gear inches and metres of development, or works backwards from a target speed to the cadence it needs.
- Circumferences printed on the page
- Full gear matrix included
- Free — no sign-up
Your gearing
Speeds assume the tyre rolls at its printed circumference with no slip — exactly how the matrix below is built.
Your results
Speed
—
| Gear ratio | — |
|---|---|
| Wheel circumference | — |
| Cadence | — |
| Speed | — |
Gear inches use the wheel diameter implied by the circumference (circumference ÷ π).
The gear matrix at 90 rpm
Every common chainring against every common cog, on a 700×25c wheel (2,105 mm) at a steady 90 rpm, in km/h. Find your cruising gear, check the jump between cogs before a cassette swap, or see what a compact 34-tooth ring really gives up at the top end. For any other cadence or wheel, run the combination through the solver above — and for the speed itself in pace terms, the bike speed calculator on the homepage converts it instantly.
Swipe sideways to see the whole matrix →
| Chainring ↓ · Cog → | 11T | 13T | 15T | 17T | 19T | 21T | 24T | 28T |
|---|---|---|---|---|---|---|---|---|
| 34T | 35.1 | 29.7 | 25.8 | 22.7 | 20.3 | 18.4 | 16.1 | 13.8 |
| 36T | 37.2 | 31.5 | 27.3 | 24.1 | 21.5 | 19.5 | 17.1 | 14.6 |
| 39T | 40.3 | 34.1 | 29.6 | 26.1 | 23.3 | 21.1 | 18.5 | 15.8 |
| 42T | 43.4 | 36.7 | 31.8 | 28.1 | 25.1 | 22.7 | 19.9 | 17.1 |
| 44T | 45.5 | 38.5 | 33.3 | 29.4 | 26.3 | 23.8 | 20.8 | 17.9 |
| 46T | 47.5 | 40.2 | 34.9 | 30.8 | 27.5 | 24.9 | 21.8 | 18.7 |
| 48T | 49.6 | 42.0 | 36.4 | 32.1 | 28.7 | 26.0 | 22.7 | 19.5 |
| 50T | 51.7 | 43.7 | 37.9 | 33.4 | 29.9 | 27.1 | 23.7 | 20.3 |
| 52T | 53.7 | 45.5 | 39.4 | 34.8 | 31.1 | 28.1 | 24.6 | 21.1 |
| 53T | 54.8 | 46.3 | 40.2 | 35.4 | 31.7 | 28.7 | 25.1 | 21.5 |
How gear speed is calculated
One turn of the cranks turns the rear wheel chainring ÷ cog times. Each wheel turn rolls the bike one circumference forward, and cadence turns per minute become an hourly distance with the × 60. With the circumference in metres the result is metres per hour — divide by 1,000 for km/h. Two older measures come from the same ratio: gear inches (ratio × wheel diameter in inches) and development (ratio × circumference, in metres per crank turn). The methodology page documents the circumference figures and the conventions behind them.
A 50-tooth chainring and 17-tooth cog on a 700×25c wheel (2,105 mm) at 90 rpm: ratio 2.94 × 2.105 m × 90 × 60 = 33.4 km/h (20.8 mph), 77.6 gear inches, 6.19 m of development per pedal turn.
Wheel circumference table
These are the circumferences the solver and matrix use — standard published values for each tyre size at typical pressures. Your exact tyre can differ by a few millimetres; a roll-out measurement (one full wheel turn with you on the bike) is the most accurate figure of all.
| Wheel and tyre | ETRTO | Circumference |
|---|---|---|
| 700×23c | 23-622 | 2,096 mm |
| 700×25c | 25-622 | 2,105 mm |
| 700×28c | 28-622 | 2,136 mm |
| 700×32c | 32-622 | 2,155 mm |
| 650B × 47 | 47-584 | 2,076 mm |
| 26″ × 2.0 | 50-559 | 2,055 mm |
| 29″ × 2.2 | 56-622 | 2,288 mm |
Gearing tells you the speed a cadence produces; it says nothing about the effort. To find the power behind any of these speeds, continue to the watts to speed calculator.
Limitations
- Speeds assume no tyre slip and a steady cadence — real riding surges and eases constantly.
- Printed circumferences are nominal. Tyre model, pressure and rider weight change the true figure slightly.
- The matrix holds cadence at 90 rpm; most riders spin slower uphill and faster downhill, which the solver covers.
Frequently asked questions
What are gear inches?
Gear inches describe how far one full pedal turn moves the bike, expressed as the diameter of an old-fashioned penny-farthing wheel that would travel the same distance. It equals the gear ratio multiplied by the wheel diameter in inches — 77.6 gear inches for a 50/17 gear on a 700×25c wheel.
What cadence should I ride at?
Most riders settle between 80 and 95 rpm on the flat. Lower cadences load the muscles harder per stroke; higher cadences shift the work to your breathing. The matrix on this page is drawn at 90 rpm — use the solver to test your own number.
Does wheel size change my speed much?
A little. Swapping a 700×25c (2,105 mm) for a 700×32c (2,155 mm) adds about 2.4% to every speed in the table — roughly 0.8 km/h at cruising pace. Chainring and cog choices move speed far more.
What gear do I need for hills?
Work backwards from the speed you can hold on the climb. At 12 km/h and 70 rpm on a 700×25c wheel you need a ratio near 1.17 — a 34-tooth chainring with a 29-tooth cog, or a 39 with a 33. The solver above runs any combination.
Why does my bike computer show a different speed?
Almost always the wheel circumference stored in the computer. If it holds a generic 700c value instead of your tyre’s real circumference, every speed and distance is off by that percentage. Measure yours with a roll-out and enter the measured figure in the computer.
Keep working the numbers
Gearing is one leg of the ride. The bike speed calculator turns any of these speeds into pace, distance and time; the watts to speed calculator prices the effort behind them; the triathlon pace calculator builds a race around your cruising gear's speed; the stationary bike calculator covers the indoor version; and the bike pace chart prints every speed and pace side by side.
Bike Speed Calculator
Any two of speed, pace, distance and time — get the other two.
Open the calculator →Watts to Speed Calculator
The power a speed takes — and the speed a power buys.
Open the calculator →Triathlon Pace Calculator
Swim, bike and run splits for Ironman, 70.3, Olympic and Sprint.
Open the calculator →Bike Pace Chart
Every speed from 10–50 km/h with mph and pace — printable.
Open the calculator →- Sheldon Brown’s gear pages — gear inches, gain ratios and development explained
- Gear inches — Wikipedia — the historical definition used here