The Gear Inch Calculator helps cyclists understand how far their bike travels with one full pedal revolution based on their gear ratio and wheel size. It is commonly used by road cyclists, mountain bikers, and track racers to evaluate gearing efficiency, optimize cadence, and fine-tune bike setups. This calculator simplifies the decision-making process for choosing gear combinations that suit different terrains or riding styles.
By entering the number of teeth on the front chainring, the number of teeth on the rear cog, and the wheel diameter, riders can estimate how “heavy” or “light” a gear feels. Higher gear inches mean the bike travels more distance per pedal revolution and feels harder to pedal, while lower gear inches mean less distance per revolution and easier pedaling.
This calculator falls under the cycling gear ratio calculator category.
formula
Gear Inch Formula:
Gear Inches = (Front Chainring Teeth ÷ Rear Cog Teeth) × Wheel Diameter
Variables Explanation:
Front Chainring Teeth is the number of teeth on the front chainring (pedal gear)
Rear Cog Teeth is the number of teeth on the rear sprocket (cassette or freewheel)
Wheel Diameter is the outer diameter of the bicycle wheel including the tire, usually measured in inches (commonly 26, 27.5, 29, or 700c which is around 27.5 inches)
Reference Table for Common Gear Inch Combinations
The following table shows sample gear inch values for different common gear combinations using a 27.5-inch wheel. This helps riders quickly estimate without doing the math.
| Front Chainring | Rear Cog | Wheel Size (inches) | Gear Inches |
|---|---|---|---|
| 50 | 25 | 27.5 | 55 |
| 40 | 20 | 27.5 | 55 |
| 36 | 18 | 26 | 52 |
| 42 | 21 | 29 | 58 |
| 52 | 13 | 27.5 | 110 |
| 34 | 28 | 27.5 | 33.4 |
Note: 700c wheels are roughly equal to 27.5 inches in diameter.
Common Conversions Useful with Gear Inch Calculations
If you need to convert 700c to inches:
700c ≈ 27.5 inches
To convert millimeters to inches:
Inches = Millimeters ÷ 25.4
If measuring wheel diameter with a tire:
Wheel Diameter = Rim Diameter + (2 × Tire Height)
Example
Let’s say you have a road bike with the following setup:
- Front Chainring Teeth: 50
- Rear Cog Teeth: 25
- Wheel Diameter: 27.5 inches
Plugging into the formula:
Gear Inches = (50 ÷ 25) × 27.5
Gear Inches = 2 × 27.5
Gear Inches = 55
This means for every full turn of the pedals, the bike moves forward as if it had a 55-inch wheel.
Most Common FAQs
For beginners, a gear inch range of 40–65 is ideal. It allows easy pedaling on flat and moderate hills. Lower gear inches make climbing easier.
Gear inches and cadence work together. High gear inches with low cadence suit speed on flat roads. Low gear inches with high cadence help in hill climbing.
No. Higher gear inches make pedaling harder, suitable for fast flat rides. But they are not good for climbing or starting. Lower gear inches give more control and comfort, especially on rough terrain.