Enter your drivetrain and wheel details to see gear inches and speed at any cadence.
Enter your drivetrain details
Fill in the form and click Calculate Gears to see your results.
Choosing the right bike gearing can make the difference between spinning comfortably up steep climbs and grinding at a painfully slow cadence. Whether you ride road, gravel, mountain bike, or bikepacking routes, understanding gear ratios and gear inches helps you determine if your drivetrain is suited for the terrain you plan to ride.
This calculator helps you understand how your chainring, cassette, wheel size, and cadence translate into real-world speed and climbing ability.
Below is a simple explanation of how these concepts work.
The gear ratio describes the mechanical relationship between the front chainring and the rear cog on your cassette.
It is calculated as:
Gear ratio = chainring teeth ÷ rear cog teeth
For example:
The gear ratio is:
40 ÷ 20 = 2.0
This means the rear wheel rotates two times for every pedal revolution.
Higher gear ratios produce more speed, while lower gear ratios make it easier to climb.
| Setup | Gear Ratio | Result |
|---|---|---|
| 40 / 10 | 4.0 | Very fast gear |
| 40 / 20 | 2.0 | Moderate gear |
| 40 / 40 | 1.0 | Climbing gear |
A lower gear ratio allows you to turn the pedals more easily when climbing steep hills or riding off-road terrain.
While gear ratio tells you the mechanical relationship between chainring and cassette, cyclists often use gear inches to compare gearing across different bikes and wheel sizes.
Gear inches estimate how far the bike travels with each pedal revolution.
The formula is:
Gear inches = gear ratio × wheel diameter
For example:
Gear inches = 28
Lower gear inches make climbing easier, while higher gear inches allow higher speeds.
| Riding Type | Typical Lowest Gear |
|---|---|
| Road bike | 30–36 gear inches |
| Gravel bike | 20–30 gear inches |
| Mountain bike | 16–25 gear inches |
| Loaded bikepacking | 16–22 gear inches |
If your lowest gear inches are too high for the terrain, you may find yourself forced to pedal extremely slowly or stand while climbing.
Cadence refers to how fast you pedal, measured in revolutions per minute (RPM).
Most cyclists pedal efficiently between:
The speed you travel depends on three things:
For example, at 90 RPM:
| Gear Ratio | Approx Speed |
|---|---|
| 1.0 | ~7 mph |
| 2.0 | ~14 mph |
| 4.0 | ~28 mph |
Your easiest gear determines how slow you can ride without dropping below a comfortable cadence. This is why climbing gears are so important.
Gravel riding often includes:
These conditions make it harder to maintain speed and traction compared to paved roads. Because of this, gravel bikes usually use lower gearing than road bikes.
| Setup | Lowest Gear Inches |
|---|---|
| Road race bike | ~34 |
| Gravel bike | ~24 |
| Bikepacking bike | ~18–22 |
Lower gearing allows riders to maintain a steady cadence while climbing rough terrain, which reduces fatigue and improves traction.
Choosing the right gearing depends on several factors:
Steeper climbs require lower gear inches.
| Terrain | Suggested Lowest Gear |
|---|---|
| Rolling gravel | 24–28 gear inches |
| Steep gravel | 20–24 gear inches |
| Bikepacking routes | 18–22 gear inches |
| Mountain bike trails | 16–20 gear inches |
Stronger riders can push slightly taller gearing, but extremely steep terrain can challenge even very fit cyclists.
If you are carrying bikepacking gear or panniers, you may want significantly lower gearing to maintain cadence while climbing.
Many riders struggle to answer questions like:
This calculator converts drivetrain specs into real-world metrics including:
You can use it to compare different setups and determine whether your gearing is appropriate for your riding style and terrain.
40T chainring + 10-44 cassette
Lowest gear: ~26 gear inches. Good for rolling gravel but can be challenging on very steep climbs.
40T chainring + 10-51 cassette
Lowest gear: ~22 gear inches. Better suited for steep gravel and bikepacking terrain.
38T chainring + 10-51 cassette
Lowest gear: ~20 gear inches. Ideal for steep dirt climbs and loaded bikepacking.
Once you understand your gearing, you can start planning rides more effectively.
If you are unsure whether your drivetrain is suitable for a particular route, try our Route Gearing Analyzer, which evaluates the steepest climbs on a route and estimates whether your current setup will allow you to maintain a sustainable cadence.