What is gear development?

Development is the distance the bike travels along the road for one full turn of the pedals. It equals the gear ratio multiplied by the wheel circumference, and it lets you compare gears across different wheel sizes directly.

What wheel diameter should I use?

Use the outside diameter of the inflated tyre, not the rim. A typical 700c road wheel with a 25mm tyre is about 668-670mm, while a 29-inch mountain wheel is roughly 736mm. The default values cover the most common setups.

What is a comfortable cadence?

Most riders are efficient between 80 and 95 RPM on flat ground, with climbers often spinning a little slower under load. Track sprinters can briefly exceed 130 RPM. Pick a cadence you can hold smoothly without bouncing in the saddle.

How do gear inches relate to development?

Gear inches express the same idea in old penny-farthing terms: ratio times wheel diameter in inches. Development in metres is the modern metric equivalent and is what this tool reports alongside speed.

Why does a bigger chainring make you faster?

A bigger front ring or smaller rear sprocket raises the gear ratio, so each pedal stroke turns the wheel further. At the same cadence that means more development and higher speed, but it also requires more force to push.

Cycling Gear Ratio & Cadence Calculator

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From cassette teeth to road speed

Your bike’s speed at any cadence is fixed by your gearing and wheel size. This calculator turns four inputs — front chainring teeth, rear sprocket teeth, wheel diameter, and cadence — into the three numbers riders actually care about: gear ratio, development (metres per pedal revolution), and resulting speed.

How it works

The maths chains three simple relationships:

ratio        = chainring_teeth / sprocket_teeth
circumference= pi * wheel_diameter_mm / 1000   (metres)
development  = ratio * circumference           (metres per pedal turn)
speed_kmh    = development * cadence_rpm * 60 / 1000

So one pedal revolution advances the wheel ratio turns, each covering one circumference. Multiply by cadence (revolutions per minute) and convert minutes to hours and metres to kilometres to get road speed.

Example and tips

A 50-tooth chainring with a 14-tooth sprocket gives a ratio of 50 / 14 = 3.57. On a 670mm wheel the circumference is about 2.10m, so development is 3.57 * 2.10 = 7.51m per stroke. At 90 RPM that is 7.51 * 90 * 60 / 1000 = 40.6 km/h. To hold the same speed in an easier gear you would spin a smaller ring or larger sprocket at a higher cadence. Always measure your real inflated tyre diameter for the most accurate speed.