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Gear Ratio Calculator

Calculate gear ratio, metres per revolution and speed at a given cadence

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๐Ÿ‡ฉ๐Ÿ‡ฐ All calculations are based on Danish rules, rates, and currency (DKK). This calculator is translated for convenience but applies exclusively to Denmark.

Calculate your gear ratio

The gear ratio calculator helps you understand the relationship between your front and rear sprockets. A gear ratio tells you how many times the rear wheel rotates for each pedal revolution, determining your speed and effort.

What is gear ratio?

Gear ratio is calculated by dividing the number of teeth on the front chainring by the number of teeth on the rear cassette. A ratio of 3.0 means the rear wheel turns 3 times for each pedal revolution. Higher ratios give higher speed but require more force, while lower ratios are easier to pedal but give lower speed.

Typical gear ratios

A road bike typically has front chainrings with 50/34 teeth and a cassette with 11-28 teeth. This gives gear ratios from about 1.2 (easy gear for hills) to about 4.5 (hard gear for flat roads). Mountain bikes typically have lower ratios with 32-38 teeth front and 10-51 rear for better climbing ability.

Gear ratio and speed

By combining your gear ratio with wheel circumference and cadence, you can calculate your speed. With a ratio of 3.33 (50/15), wheel circumference of 210 cm and cadence of 90 rpm, you ride at about 37.8 km/h. This calculation helps plan which gears to use in different situations.

Frequently Asked Questions

What is a good gear ratio for hills?

For hills, a gear ratio below 1.5 is recommended, ideally around 1.0-1.2. This is typically achieved with a 34T front chainring and 28-34T rear cassette. For steep hills (over 10% gradient), a ratio below 1.0 may be necessary, e.g. 34/36.

How does wheel size affect speed?

Larger wheels (greater circumference) cover more distance per pedal revolution at the same gear ratio. A 700c road wheel has a circumference of about 210 cm, while a 650b wheel is about 200 cm. The 5% difference in circumference gives about 5% difference in speed at the same cadence and gear ratio.

What does 50/34 and 11-28 mean in gear context?

50/34 refers to the two front chainrings with 50 and 34 teeth respectively. 11-28 refers to the rear cassette, where the smallest sprocket has 11 teeth and the largest 28. A compact crank (50/34) is popular for recreational cyclists as it provides an easier gear for hills than a standard (53/39). Cassettes with wider range like 11-32 or 11-34 are great for hilly routes.

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