Bike Gear Ratio Calculator
Enter your bike setup to calculate gear ratio, gear inches, gain ratio, rollout (development), and estimated speed at your cadence.
Why gear ratio matters for cyclists
A bike’s gearing determines how hard you need to push on the pedals and how fast the bike moves for each pedal revolution. The right setup can make climbing easier, improve flat-road efficiency, and help you control cadence during long rides. This gear ratio bike calculator gives you practical numbers that riders actually use: ratio, gear inches, rollout, gain ratio, and speed.
How to use this calculator
- Front chainring teeth: Number of teeth on your selected front ring.
- Rear cog teeth: Number of teeth on the selected cassette sprocket.
- Wheel diameter: Effective wheel diameter in inches (including tire).
- Cadence: Your pedal speed in RPM.
- Crank length: Needed for gain ratio, typically 165–175 mm.
Click Calculate to see your output instantly. Use Reset to return to defaults.
Key formulas used
Gear Inches = Gear Ratio × Wheel Diameter (in)
Development (Rollout) = Wheel Circumference × Gear Ratio (meters per crank revolution)
Speed (km/h) = Development × Cadence × 60 / 1000
Gain Ratio = (Wheel Radius / Crank Length) × Gear Ratio
Understanding your results
Gear Ratio
This is the simplest representation of your selected gear. Higher numbers are harder but faster; lower numbers are easier and better for steep climbs.
Gear Inches
Gear inches are a traditional way to compare gearing across bike types. A larger gear-inch number means more distance per pedal turn.
Development (Rollout)
Development tells you exactly how far the bike moves with one full pedal revolution. This metric is especially useful for training and pacing.
Estimated Speed
Speed is calculated from your cadence and chosen gear. Real speed will vary with wind, terrain, tire pressure, and rider position.
Quick gearing guide by riding style
| Riding Type | Typical Goal | Common Gear Preference |
|---|---|---|
| Steep Climbing | Keep cadence comfortable uphill | Lower ratio (small front / large rear) |
| Endurance Road | Steady effort over long distance | Moderate ratio with smooth cadence |
| Fast Flat Riding | Higher cruising speed | Higher ratio (large front / small rear) |
| Gravel / Mixed Terrain | Versatility across surfaces | Wide range cassette and balanced ratio |
Practical tips for choosing better gears
- Target a cadence range you can sustain (many riders sit around 80–100 RPM).
- For hilly routes, prioritize easier climbing gears over top-end speed.
- Compare development values across gears to spot overlaps and gaps.
- Use gain ratio when comparing bikes with different wheel or crank sizes.
FAQ
What is a good gear ratio for beginners?
Beginners typically benefit from lower to moderate ratios because they reduce pedal force and help maintain smooth cadence, especially on hills.
Is gear inches better than gear ratio?
Neither is strictly better. Gear ratio is quick and simple, while gear inches are easier for comparing setups across different wheel sizes.
Why does my real-world speed differ from the calculator?
The calculator assumes ideal conditions. Wind, road gradient, tire deformation, drivetrain losses, and body position all affect actual speed.
Final thoughts
The best bike gearing is the one that matches your fitness, terrain, and riding goals. Use this calculator to test combinations before changing chainrings or cassette sizes. Even small adjustments can dramatically improve comfort and efficiency on the road or trail.