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Cadence to Speed Calculator

Converts pedalling cadence into road speed from the gear ratio (or chainring and cog teeth) and the wheel circumference, giving km/h, mph, m/s, metres per pedal revolution and wheel rpm.

When to use

You want the speed a given cadence produces in a known gear, e.g. to plan cadence targets on a trainer or check a bike computer's wheel-size setting.

Do not use when: You need to derive the gear ratio and wheel size from teeth counts and tyre dimensions first (use bike-gear-ratio), or you want running pace conversions (use pace-converter).

Formula

gear_ratio = chainring_teeth / cog_teeth (if not given); development_m = gear_ratio × wheel_circumference_mm / 1000; speed_kmh = cadence_rpm × development_m × 60 / 1000; speed_mph = speed_kmh / 1.609344

Assumes no wheel slip and a fixed ratio; for internally geared hubs multiply gear_ratio by the hub's stage ratio. Measured roll-out circumference (mark the tyre, roll one revolution under rider weight) is more accurate than tabulated values by 1–2 %.

Inputs

Parameter	Type	Unit	Required	Description
`cadence_rpm`	number	rpm	yes	Pedal revolutions per minute. Range: ≥ 1, ≤ 250
`gear_ratio`	number		no	Chainring teeth divided by cog teeth (wheel turns per crank turn). Give this or chainring_teeth and cog_teeth. Range: > 0, ≤ 15
`chainring_teeth`	integer	teeth	no	Front chainring teeth, used with cog_teeth when gear_ratio is not given. Range: ≥ 10, ≤ 90
`cog_teeth`	integer	teeth	no	Rear sprocket teeth, used with chainring_teeth when gear_ratio is not given. Range: ≥ 6, ≤ 60
`wheel_circumference_mm`	number	mm	default 2111	Rolling circumference of the wheel with tyre: about 2111 mm for 700×25C, 2096 for 700×23C, 2288 for 29×2.1", 2055 for 26×2.0". Range: ≥ 500, ≤ 3000

Outputs

Output	Type	Unit	Description
`speed_kmh`	number	km/h	cadence × gear ratio × circumference.
`speed_mph`	number	mph	Same speed in miles per hour.
`speed_m_per_s`	number	m/s	Same speed in metres per second.
`development_m`	number	m	gear_ratio × wheel_circumference_mm / 1000.
`wheel_rpm`	number	rpm	cadence_rpm × gear_ratio.
`gear_ratio_used`	number		Ratio applied (given directly or chainring_teeth / cog_teeth).

Example

90 rpm in a 2.0 ratio (50 × 25), 700×25C: {"cadence_rpm":90,"gear_ratio":2} → {"speed_kmh":22.8,"speed_mph":14.17,"speed_m_per_s":6.333,"development_m":4.222,"wheel_rpm":180,"gear_ratio_used":2}

100 rpm in 53 × 11, 700×23C: {"cadence_rpm":100,"chainring_teeth":53,"cog_teeth":11,"wheel_circumference_mm":2096} → {"gear_ratio_used":4.818,"development_m":10.099,"speed_kmh":60.59,"speed_mph":37.65}

GET https://tttkmbb.com/api/v1/calculate/cadence-to-speed?cadence_rpm=90&gear_ratio=2

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/cadence-to-speed (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/cadence-to-speed · Markdown: https://tttkmbb.com/fitness/cadence-to-speed.md · JSON definition: https://tttkmbb.com/fitness/cadence-to-speed.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="cadence-to-speed"
OpenAPI operationId: convert_cadence_to_speed
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Which input wins if I give both gear_ratio and teeth counts?

gear_ratio is used and the teeth counts are ignored.

What cadence is normal?

Most trained road cyclists ride at 80–100 rpm; climbing is often 60–80 rpm. Speed scales linearly with cadence in a fixed gear.

Related calculators

Bike Gear Ratio Calculator — Derive the ratio and circumference from teeth counts, rim and tyre size.
Pace Converter — Convert speed to pace units.
Speed Converter — General speed unit conversion.