Bicycle Gear Ratio & Gear Inches Calculator
Last updated: 2026-06-25
Gear ratio = chainring teeth ÷ sprocket teeth. Gear inches = gear ratio x wheel diameter (inches). Development = wheel circumference x gear ratio (distance per pedal revolution).
Enter the front/rear teeth and wheel size to see gear ratio, gear inches, development and speed at 90 rpm cadence all at once.
Enter gear info
Gear ratio
0.00
| Item | Value |
|---|---|
| Gear ratio (front ÷ rear) | |
| Gear inches | |
| Development (per pedal revolution) | |
| Wheel circumference | |
| Speed at cadence |
Gear inches and development are approximations based on nominal wheel diameter. Actual values vary slightly with tire width, pressure and rim spec (ETRTO).
How to use
- Enter teeth — Enter the front chainring teeth and the rear sprocket (cog) teeth.
- Pick wheel size — Select your bike's wheel size (700c/29, 27.5, 26, 24, 20 inch).
- Read the result — Press Calculate to show gear ratio, gear inches, development and speed at the given cadence in a table.
How to calculate gear ratio, gear inches and development
Three metrics compare bicycle gears. Gear ratio shows the pedal-to-rear-wheel relationship from the teeth alone, gear inches factor in wheel size to compare different bikes, and development (rollout) shows the actual distance traveled per pedal revolution in meters.
| Metric | Formula | Meaning |
|---|---|---|
| Gear ratio | chainring ÷ sprocket | Rear-wheel turns per pedal revolution |
| Gear inches | gear ratio x wheel diameter (inches) | Wheel-size-adjusted gear heaviness |
| Development | wheel circumference (m) x gear ratio | Distance per pedal revolution (m) |
| Speed | development x cadence x 60 ÷ 1000 | Speed (km/h) at that cadence |
For reference, nominal wheel diameters used are 700c/29 inch ≈ 26.3", 27.5 inch ≈ 27.5", 26 inch ≈ 26", 24 inch ≈ 24", 20 inch ≈ 20". Wheel circumference is diameter x π x 0.0254 (m). For example, 50T·14T·700c gives a gear ratio of 3.57 and about 94" gear inches.
Check the workload for your gear setup with the cycling calorie calculator, and to prepare gears for a route's gradients, see the difficulty table on bike routes.
Frequently asked questions (FAQ)
How is gear ratio calculated?
Gear ratio is the front chainring teeth divided by the rear sprocket teeth. For example, a 50T chainring and 14T sprocket give 50 ÷ 14 ≈ 3.57, meaning the rear wheel turns about 3.57 times per pedal revolution. A larger value is a harder, faster gear.
What are gear inches?
Gear inches multiply the gear ratio by the wheel diameter (inches), equivalent to the front-wheel diameter of a directly driven penny-farthing. They let you compare gears on bikes with different wheel sizes on the same basis, usually between about 20 and 125.
What is development (rollout)?
Development is the distance (meters) the bike actually travels per pedal revolution. It equals wheel circumference x gear ratio, which is the same as gear inches x π x 0.0254. It's useful for intuitively comparing gear heaviness in metric units.
How does wheel size affect the result?
Gear ratio itself depends only on the teeth and is independent of wheel size, but gear inches, development and speed are proportional to wheel diameter. With the same teeth, a 700c/29-inch wheel has larger gear inches and travels farther per revolution than a 26-inch wheel.
How should I set the gear ratio for climbing?
On climbs, a lower (easier) gear ratio helps. Use a smaller chainring in front and a larger sprocket in back to lower the ratio to around 1.0 or below, so you can keep a higher cadence with the same effort and reduce knee strain.
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Last updated: 2026-06-25