Bike Gear Ratio Calculator
Use this free bike gear ratio calculator to find your gear ratio, gear inches, and development from your chainring, rear cog, and wheel size. Enter your numbers and the results update instantly โ no sign-up needed.
Enter your numbers
Use 27 for a standard 700c road wheel.
Used to estimate your speed at this cadence.
Your results
How to use this calculator
Count the teeth on your front chainring and on the rear cog you are using, then enter them above. A standard 700c road wheel is 27 inches in diameter, so the default works for most road bikes; change it if you ride a 26-inch, 29er, or other wheel size.
If you know your typical pedaling cadence in revolutions per minute, enter it to estimate how fast this gear moves you. Try your smallest rear cog for your top speed gear and your largest cog for your easiest climbing gear, then compare the ratios to feel the difference before you shift.
How it works
The gear ratio is simply the chainring teeth divided by the cog teeth: gear ratio = chainring รท cog. A 50-tooth chainring with an 11-tooth cog gives 50 รท 11 = 4.55, meaning the rear wheel turns 4.55 times for each full crank revolution. It is exact arithmetic, not an estimate.
Gear inches fold your wheel size into the ratio: gear inches = gear ratio ร wheel diameter (inches). With a 4.55 ratio and 27-inch wheels, that is 4.55 ร 27 โ 122.7 inches. It describes the gear as the diameter of an equivalent direct-drive wheel.
Development is the distance the bike rolls with one crank turn: development = gear inches ร ฯ. The example above works out to about 385.6 inches, or 32.1 feet, per pedal revolution. Speed at a given cadence follows from development: speed (mph) = development in inches ร cadence (rpm) ร 60 รท 63,360.
Assumptions: a perfect rigid wheel (tire compression ignored), direct drive with no slipping, and a constant cadence. Real-world speed varies with tire pressure, surface, wind, and effort.
Frequently asked questions
What is a good bike gear ratio?
There is no single best ratio โ it depends on terrain and fitness. A 50/11 combo (4.55) is a fast road gear for flats and descents, while a 34/28 combo (1.21) is an easy climbing gear. Lower ratios spin easier for hills; higher ratios move you faster per pedal stroke.
What are gear inches?
Gear inches combine your gear ratio with your wheel size into a single number: gear ratio multiplied by the wheel diameter in inches. A classic 700c road setup with a 50/11 gear gives about 123 gear inches. Higher gear inches mean a harder, faster gear.
What is development in cycling?
Development is the distance your bike travels with one full turn of the cranks, in inches or feet. It equals gear inches times pi. A 50/11 gear on 27-inch wheels has a development of about 386 inches (32.1 feet) per pedal revolution.
How do I compare two gears to see which is easier?
Divide their gear ratios. For example, a 50/11 gear (4.55) divided by a 34/28 gear (1.21) is about 3.8, so the climbing gear is roughly 3.8 times easier to turn than the top gear. Lower ratios always mean less effort per pedal stroke.
How do I count the teeth on my chainring and cog?
Count every tooth on the front chainring (the ring your pedals drive) and every tooth on the rear cog you are using. Common road chainrings are 50/34 teeth, and rear cassettes run from about 11 to 34 teeth. Mark one tooth with tape and count all the way around to be sure.