Bike Gear Ratio Calculator
Enter your wheel diameter, chainring and cog teeth, and pedaling cadence to calculate gear inches and resulting speed.
Last updated: September 5, 2026
Frequently asked questions
What are 'gear inches'?
A standard way to compare bike gearing across different wheel sizes and gear combinations - it's the effective diameter (in inches) of the wheel if it were driven directly by the pedals with a 1:1 ratio, calculated as wheel diameter × (chainring teeth ÷ cog teeth).
How do I calculate speed from cadence and gearing?
Each pedal revolution moves the bike forward by (gear inches × π) - multiply that by your cadence (revolutions per minute) to get distance per minute, then convert to your preferred speed unit.
What's a typical gear-inch range for road cycling?
Roughly 20-30 gear inches for steep climbs up to 100-130+ gear inches for fast flat riding or descents, depending on rider strength and terrain - a wide range across a bike's full gear set covers climbing to sprinting.
Does this account for real-world factors like tire slip or drivetrain loss?
No - it's an idealized calculation assuming no wheel slip and perfectly efficient power transfer, which is a reasonable approximation for most road and trail conditions but won't be perfectly exact.
What speed does 90 rpm cadence produce with a 50/14 gear on a 27-inch wheel?
About 26 mph - the gear inches are 27 × (50÷14) ≈ 96.4, each pedal revolution covers 96.4 × π ≈ 302.9 inches, and at 90 rpm that's 27,264 inches per minute, which converts to roughly 25.8 mph.
Why do gear inches use the wheel diameter instead of the tire's actual rolling diameter?
This calculator uses the nominal wheel diameter you enter as an approximation - the true rolling diameter (which includes tire size and slight compression under load) differs slightly, so gear-inch figures are a standardized comparison tool rather than a precise real-world distance measurement.
Is 'gear inches' the same measurement as 'development' or 'roll-out' used in some cycling computers?
They're related but not identical - development (or roll-out) is the actual distance traveled per pedal revolution, typically given in meters or inches, while gear inches is a slightly different traditional unit (effective wheel diameter). Development equals gear inches × π, which is exactly the relationship this calculator uses internally to derive speed.