Bike Gear & Cadence Speed Calculator
Find your cycling speed from chainring, cog, cadence and wheel size, with gear inches and meters of development.
Speed
33.5 km/h · 20.8 mph
- Gear ratio
- 2.94
- Development (per crank turn)
- 6.21 m
- Gear inches
- 77.8
- Wheel circumference used
- 2,111 mm
Tires flatten a little under load, so real speed runs about 1–2% lower; for exact numbers, measure your wheel's rollout and use a custom circumference.
Speed in this gear at other cadences
| Cadence | km/h | mph |
|---|---|---|
| 60 rpm | 22.4 | 13.9 |
| 70 rpm | 26.1 | 16.2 |
| 80 rpm | 29.8 | 18.5 |
| 90 rpm | 33.5 | 20.8 |
| 100 rpm | 37.3 | 23.1 |
| 110 rpm | 41 | 25.5 |
Show the work
Wheel circumference (ISO 5775 size)
C = π × (bead-seat diameter + 2 × tire width)
π × (622 + 2 × 25) = 2,111.150263 mm
Distance per crank turn (development)
dev = chainring ÷ cog × C ÷ 1,000
50 ÷ 17 × 2,111.150263 ÷ 1,000 = 6.20926548 m
Speed, to 1 decimal
km/h = dev × cadence × 60 ÷ 1,000; mph = km/h × 1,000 ÷ 1,609.344
6.20926548 × 90 × 60 ÷ 1,000; 33.53003359 × 1,000 ÷ 1,609.344 = 33.5 km/h · 20.8 mph
How it works
Speed = cadence × (chainring ÷ cog) × wheel circumference; circumference ≈ π × (bead-seat diameter + 2 × tire width) (ISO 5775 sizes); gear inches = ratio × wheel diameter in inches
Questions
- How does the bike gear & cadence speed calculator work?
- Speed = cadence × (chainring ÷ cog) × wheel circumference; circumference ≈ π × (bead-seat diameter + 2 × tire width) (ISO 5775 sizes); gear inches = ratio × wheel diameter in inches.
- What do I need to enter?
- Chainring teeth, Cog teeth, Cadence, Wheel and tire, Wheel circumference. Optional fields can be left blank.
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