Bike Speed Calculator
Calculate bicycle speed from cadence, gear ratio, and wheel diameter.
How to Calculate Bike Speed from Cadence
This Bike Speed Calculator estimates how fast you ride based on pedaling cadence, gear ratio, and wheel size. Enter your RPM, chainring and cog teeth, and wheel dimensions to get speed in km/h or mph. For related cycling tools, try our Bike Cadence and Speed Calculator.
The Bike Speed Formula
Speed = π × (d + 2t) × (Nchainring / Ncog) × cadence / 60, where d is wheel diameter in inches, t is tire width in inches, and cadence is in RPM. The result gives linear speed in meters per second, converted to km/h or mph. A 29" fixie at 2.75:1 gear ratio and 70 RPM reaches about 27 km/h.
Gear Ratio and Cadence
Higher gear ratios (larger front chainring or smaller rear cog) translate each pedal revolution into more wheel rotation, increasing speed at the same cadence. Most riders maintain 60 to 100 RPM comfortably. Sprint efforts may reach 110 RPM briefly with the right gear selection.
Frequently Asked Questions
How do I calculate bike speed from cadence?
Multiply wheel circumference by gear ratio and cadence. Use speed = π × diameter × gear ratio × RPM / 60, then convert to km/h (× 3.6) or mph (× 2.237).
What cadence is best for cycling?
Most recreational riders aim for 60 to 100 RPM. Higher cadence with lower gears reduces muscle strain, while lower cadence with higher gears suits short sprints.
Does a higher gear mean faster speed?
Yes, at the same cadence a higher gear ratio produces more speed. It also requires more torque from your legs, so choose gears that balance speed and sustainable effort.
What wheel size should I use?
Measure the labeled wheel size (e.g. 29", 27.5", 700c) and add twice the tire width for rolling diameter. Road bikes often use 700c wheels; mountain bikes commonly use 27.5" or 29".
How fast is 70 RPM on a fixie?
On a 29" wheel with a 2.75:1 gear ratio, 70 RPM produces roughly 27 km/h (17 mph). Actual speed varies with exact tire width and pressure.
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