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Gear Ratios

Learn about the fundamental gearing system on a bicycle

Gearing systems are an important component of bicycle design. This article aims to explain what gear ratios are, how they're calculated, and when they're useful.

What are gear ratios?

Gear ratio is the ratio of the chainring size to the sprocket size, or in other words, it's the ratio of revolutions of the pedals to revolutions of the rear wheel.

How are gear ratios calculated?

This system is the easiest to calculate. It's expressed as a ratio and thus independent of units. It's calculated by dividing the number of teeth on the front cog by the number of teeth on the rear cog.

Gear ratios can be calculated from the following formula, where CT stands for chainring teeth, ST for sprocket teeth, and GR for gear ratios.

CT / ST = GR

When should gear ratios be used?

Gear ratio is the most simple system when it comes to comparing gearing on bicycles. However, it's less effective when the wheel sizes differ, nor when the crank arms are of different lengths. It's recommended to use gear ratios prior to changing the cassette.

Which other gearing systems exist?

There exists several other systems, each with their advantages and drawbacks. To learn more about these gearing systems, please visit our articles covering each topic individually.

Why does BikeCalc provide all gearing systems?

BikeCalc tries to cater for all cyclists and modern bicycles. We realize that no system is better than an other, only some are better suited in certain circumstances; and it's up to the end-user to decide which one is most appropriate for their specific use case.