HesapHanem

Cadence to Speed Calculator

Enter cadence, gear ratio and wheel circumference to get your speed in km/h and mph.

How it is calculated

Each pedal turn spins the rear wheel gear ratio times, and each wheel turn rolls forward one wheel circumference. Speed is km/h = cadence × gear ratio × circumference × 60 ÷ 1000, with cadence in pedal revolutions per minute, the gear ratio as chainring teeth ÷ cog teeth, and the circumference in metres. The 60 turns minutes into hours and the 1000 turns metres into kilometres. Miles per hour is km/h × 0.621371. If the circumference is left empty, the tool uses 2.105 m. Cadence cannot be negative; gear ratio and circumference must be above zero. The result assumes no drivetrain losses, no coasting and no tyre slip.

Worked example

A rider pedals at 90 rpm with a 50-tooth chainring and a 17-tooth cog, a ratio of 50 ÷ 17 ≈ 2.94. The wheel circumference is 2.105 m. Metres per minute: 90 × 2.94 × 2.105 = 557.0. Per hour: 557.0 × 60 = 33,419 m, which is 33.42 km/h. In miles per hour: 33.42 × 0.621371 = 20.77 mph. In a gear one cog larger, the same cadence would give a lower speed.

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Common mistakes

  • Typing the wheel diameter or the tyre size in millimetres. The circumference field is in metres, for example 2.105, not 2105.
  • Entering the gear as two numbers, such as 50/17. Divide first and enter about 2.94.
  • Inverting the ratio (cog ÷ chainring), which gives a value below 1 and a very low speed.
  • Using a wheel circumference from a different tyre size. A wider tyre rolls farther per turn, so the speed changes.
  • Expecting the figure to match a bike computer during a climb or in a headwind. It is a theoretical speed from cadence, not measured by GPS.

About this calculator

A cyclist's road speed comes from three factors multiplied together: pedalling cadence (rpm), the gear ratio (chainring teeth ÷ cassette cog teeth), and the wheel circumference. Each pedal revolution turns the rear wheel by the gear ratio, and each wheel revolution covers one circumference of ground.

This calculator chains those together — cadence × gear ratio × wheel circumference, adjusted for units and time — to output speed in both km/h and mph. Cyclists and coaches use it to plan gear selection for a target speed, or to understand why a given cadence feels faster in a taller gear.

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Comments (1)

  • Editorial team

    The number you get is a ceiling for real riding, because it assumes you pedal the whole time. A useful check is a steady, flat, windless stretch with a GPS head unit: if it reads clearly lower than this result at the same cadence and gear, the circumference you entered is probably too large for your tyre. Rolling the wheel one turn on the floor and measuring beats a chart. Which tyre size are you running, and how close did the numbers come?

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