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Bike Gear Calculator

Created by Hanna Pamuła, PhD
Reviewed by Bogna Szyk and Steven Wooding
Last updated: Jan 18, 2024


Our bike gear calculator may help you in choosing chainrings and cogs. Many contemporary bicycles have multiple gears and thus many possible bike gear ratios. Select the range of gear teeth and check which combination best suits your cycling preferences and conditions. As a result, you will get the tables in gear ratio and gear inches units.

What is a gear ratio and gear inches?

Gears are used to increase the force or speed and gear ratio is a unit of bike gearing. To calculate the gear ratio, divide the number of teeth on the front chainring by the number of teeth in a rear sprocket:

gear ratio = (number of teeth in front chainring) / (number of teeth in rear sprocket)

For example, if the number of teeth is even, the gear ratio equals 1. For 50 teeth in front and 25 in the back, the gear ratio is 2.

For bicycles equipped with hub gears, the gear ratio also depends on the internal planetary gears within the hub, so gear ratio is not a good measure when planetary gears are involved.

Gear inches is another relative measure of bicycle gearing. It corresponds to the diameter of the main wheel of an old-fashioned penny-farthing bicycle with equivalent gearing. Gear inches are calculated as the gear ratio multiplied by wheel diameter (in inches) and are usually rounded to the nearest whole number:

gear inches = wheel diameter × (number of teeth in front chainring) / (number of teeth in rear sprocket)

Why don't we use the chainring and rear sprocket teeth values as a measure of a gear? Let's answer with the question: do you know instantly that 39/14 is the same gear as a 53/19? Probably not. That way of showing the ratio is inconvenient and can be confusing. One value explaining that the gear ratio (or gear inches) for both combinations equals 2.79 (or 78) is much easier.

How does the bike gear ratio calculator work?

Our bike gear calculator can show the ratios for the range of chainrings and cogs teeth so that you can check your bike gear ratios and gear inches in different settings:

  1. Choose the minimal value of the teeth in the chainring. Let's say it's 42.

  2. Pick the maximum number, 48, for example.

  3. Analogically, select the range for cogs teeth, for instance, 10 to 24.

  4. If you want to see not only the gear ratio but also the gear inches table, enter the wheel diameter in inches.

  5. Great! The bike gear calculator displayed two nice tables with gear ratios and gear inches for all combinations in chosen range.

Ready for a bike trip? Check our other calculators for cyclists, such as calories burned biking, biking life gain calculator, or the car vs. bike calculator.

FAQ

What is a fixed gear bike?

A fixed-gear bike, often called a "fixie," is a bicycle with a single gear that doesn't have a freewheel mechanism. This means the pedals are constantly in motion when the bike is moving. Unlike traditional bikes, you can't coast on a fixie; if the bicycle is in motion, you must pedal. It offers a unique riding experience, often favored for its simplicity and direct connection between rider and road.

Which cog is gear 1 on a bike?

Gear 1 on a bike, commonly known as the "lowest" or "easiest" gear, is typically associated with the largest cog on the rear cassette and the smallest chainring on the front. This combination provides the least resistance, making it ideal for uphill climbs or starting from a stop, but it results in slower speeds.

How to calculate bike gear ratio?

To calculate the bike gear ratio, you have to follow this instruction:

  1. Identify chainring teeth: Count the teeth on the front chainring.
  2. Identify cassette teeth: Count the teeth on the rear cog or cassette.
  3. Calculate ratio: Divide the chainring teeth by the cassette teeth.
  4. Result: A higher ratio indicates more force but less speed, and vice versa.

How to replace gear shifter on a bike?

To replace the gear shifter on a bike, you have to:

  1. Remove cables: Disconnect shifter cables.
  2. Loosen clamp: Loosen the clamp, securing the shifter, using a suitable tool.
  3. Remove shifter: Slide the old shifter off the handlebar.
  4. Install new shifter: Position the new shifter, then tighten its clamp.
  5. Reconnect cables: Re-attach and adjust the cables for smooth shifting.
Hanna Pamuła, PhD
Chainring (front gears)
Min
teeth
Max
teeth
Cog (rear gears)
Min
teeth
Max
teeth
Wheel diameter
in
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