Bicycle Speed Cadence Calculator: How It Works

This calculator works out your bike speed from your cadence (pedal revolutions per minute), wheel size, and gear ratio. You enter your cadence, wheel diameter, and gear teeth counts (or gear inches), and it returns your speed in km/h or mph, plus your gear inches and development (distance per pedal stroke).

Formula

The speed is calculated from three factors: cadence (how fast you pedal), gear ratio (chainring teeth divided by rear sprocket teeth), and wheel circumference (which depends on wheel diameter). The formula is:

Speed (km/h) = Cadence (rpm) × (Front teeth / Rear teeth) × Wheel circumference (m) × 60 / 1000

Where:

• Cadence = pedal revolutions per minute (rpm)
• Front teeth = number of teeth on the front chainring
• Rear teeth = number of teeth on the rear sprocket
• Wheel circumference = Ï€ × wheel diameter (including tire) in meters
• 60 converts minutes to hours
• 1000 converts meters to kilometers

For miles per hour, replace the final conversion: multiply by 60 (minutes to hours) and divide by 1609.34 (meters per mile).

Worked Example

Using the defaults: Cadence = 90 rpm, Wheel diameter = 27.5 inches, Front chainring = 50 teeth, Rear sprocket = 15 teeth.

1. Gear ratio = 50 / 15 = 3.333
2. Wheel diameter in meters = 27.5 × 0.0254 = 0.6985 m
3. Wheel circumference = π × 0.6985 = 2.194 m
4. Distance per pedal revolution = 3.333 × 2.194 = 7.313 m
5. Distance per minute = 7.313 × 90 = 658.2 m/min
6. Distance per hour = 658.2 × 60 = 39,492 m/h
7. Speed = 39,492 / 1000 = 39.5 km/h

The calculator shows 39.5 km/h, which matches.

Why Cadence Matters

Cadence is the number of times you turn the cranks per minute. Most recreational cyclists pedal at 60–80 rpm, while experienced riders often maintain 80–100 rpm on flats. A higher cadence with a lower gear reduces stress on knees and uses your cardiovascular system more; a lower cadence with a higher gear builds muscle strength but can fatigue legs faster. Knowing your speed at a given cadence helps you choose gears for training targets or commute timing.

How to Use the Calculator

Enter your typical cadence (or use a bike computer to measure it), your wheel diameter (including tire – most road bikes use 700c ≈ 29 inches, mountain bikes 27.5 or 29 inches), and the teeth counts on your front chainring and rear sprocket. The result is your theoretical speed, assuming no wind, no gradient, and 100% drivetrain efficiency. Real-world speed will be lower due to rolling resistance, air drag, and friction.

For a multi-gear bike, you can run the calculation for each gear combination to see your speed range at a fixed cadence. Many riders use this to plan a route: if you know your comfortable cadence, you can estimate how fast you’ll go on flat ground.

Common Mistakes and Limitations

• Wheel diameter vs. wheel radius: The calculator uses diameter, not radius. If you measure from the axle to the ground, double it.
• Tire width: The diameter includes the tire. A 700×23c tire is about 29 inches, but a 700×32c is slightly larger. Use the actual measured diameter for accuracy.
• Gear inches vs. gear ratio: Gear inches (front teeth / rear teeth × wheel diameter) is a traditional measure of how “hardâ€� a gear is. The calculator gives both gear inches and development (distance per pedal stroke) for comparison.
• Cadence measurement: Cadence sensors are more accurate than estimating. If you don’t have one, count pedal revolutions for 15 seconds and multiply by 4.
• Real-world factors: The calculator ignores wind, rolling resistance, and drivetrain losses. On flat, calm roads, actual speed is typically 5–10% lower than theoretical.

Alternatives and Related Measurements

If you want to calculate speed from power (watts) instead of cadence, you need a power meter and a formula that accounts for air density, frontal area, and rolling resistance – that’s beyond a simple cadence calculator. For training, many cyclists use a “gear ratio calculator� to compare gear combinations, or a “speed calculator� that uses time and distance. This cadence-based approach is useful for understanding how gearing affects speed at a given pedal rate.

Frequently Asked Questions

What is a good cadence for cycling?

Most recreational cyclists naturally pedal at 60–80 rpm. Competitive road cyclists often aim for 80–100 rpm to reduce muscle fatigue. A cadence below 60 rpm puts more strain on knees, while above 100 rpm can raise heart rate excessively. The “best� cadence depends on your fitness, terrain, and personal comfort.

How do I measure my wheel diameter?

Measure the distance from the ground to the center of the wheel axle (the radius) and double it. Include the tire. A typical road bike wheel (700c) with a 25mm tire measures about 27.5 inches (actually 27.5–28 inches depending on tire). Mountain bike wheels are commonly 27.5 or 29 inches. For exact numbers, check the tire sidewall – it often lists the diameter in mm (e.g., 622mm for 700c).

Does gear inches matter for speed?

Gear inches is a relative measure of how far the bike travels per pedal revolution. A higher gear inch means more distance per revolution, so at the same cadence you go faster, but it requires more force. It’s a useful way to compare gears across different bikes because it normalizes wheel size.

Why is my actual speed lower than the calculator?

The calculator assumes perfect efficiency and no resistance. In reality, you lose speed to aerodynamic drag (which increases with the square of speed), rolling resistance of tires, friction in the drivetrain, and any headwind or gradient. On a flat road with no wind, you might see 90–95% of the theoretical speed.

Can I use this calculator for a stationary bike?

Yes, if you know the wheel diameter and gear ratio. However, many stationary bikes have a fixed resistance and don’t have real gears – the “speed� is simulated. In that case, the calculator gives you a theoretical speed that may not match the bike’s display.

How do I convert the result to mph?

Multiply the speed in km/h by 0.621371. For example, 39.5 km/h × 0.621371 = 24.5 mph. If you want the calculator to output mph directly, you can change the formula to divide by 1609.34 instead of 1000, but the current version gives km/h as the primary output.

Related

• Active Pace Running Calculator: Pace, Time and Distance
• Active Pace Calculator: Running Pace and Speed
• 4L80E Gear Ratio Calculator and Transmission Specs

in t | Cadence | rpm | 90 | 30
in d | Wheel diameter | inches | 27.5 | 12
in f | Front chainring teeth | teeth | 50 | 20
in r | Rear sprocket teeth | teeth | 15 | 5
out speed | Speed | km/h | (t * (f / r) * (d * 0.0254 * pi) * 60) / 1000 | 1
out gear_in | Gear inches | inches | (f / r) * d | 1
out dev | Development | m | (f / r) * (d * 0.0254 * pi) | 2