The bike gear ratio calculator shows your speed at different cadences for any chainring and cog combination. Compare gearing options for climbing, sprinting, or cruising — supports road bikes (700c), mountain bikes (29"/27.5"/26"), and any wheel size.
Gear Setup
Gear Ratio: —
Wheel circ: —| Cadence (RPM) | Speed (mph) | Speed (km/h) |
|---|
Gear Inches
Gear inches: —
Gear inches = (chainring / cog) × wheel diameter in inches. A standard benchmark for comparing gearing across different wheel sizes.
How to Use the Bike Gear Ratio Calculator
Understanding your bike's gear ratios helps you choose the right cassette or chainring for your riding style and terrain. Whether you're gearing up for a hilly sportive or building an MTB for technical terrain, this calculator shows exactly what speed you'll achieve at different cadences.
Step 1: Count Your Teeth
Count the teeth on your front chainring and the specific rear cog you want to analyze. Alternatively, look for the numbers stamped on the chainring or printed in your bike's specs (e.g., "50/34" chainset, "11-32t" cassette). For this calculator, enter one chainring/cog combination at a time to analyze that specific gear.
Step 2: Select Your Wheel Size
700c road wheels have a 2096mm tire circumference (typical 700x25c tire). 29-inch MTB wheels are slightly larger due to wider tires. 27.5-inch wheels (650b) are smaller, making them spin up faster. 26-inch wheels are the smallest MTB standard. Select the closest match to your actual wheel and tire setup.
Step 3: Interpret the Speed Table
The table shows your speed at 60, 70, 80, 90, and 100 RPM. Most recreational cyclists pedal at 70-80 RPM; trained cyclists often ride at 90-100 RPM. If the speed at 90 RPM is slower than your typical riding speed, you need a harder gear. If you can't maintain 70 RPM on climbs, you need an easier gear with fewer chainring teeth or more cog teeth.
FAQ
Is this bike gear ratio calculator free?
Yes, completely free with no account required. Calculate speed at any cadence for any gear combination instantly.
What is gear ratio in cycling?
Gear ratio is the number of rear wheel rotations for every full pedal rotation. It's calculated by dividing chainring teeth by cog teeth. A 50t chainring with a 17t cog gives a ratio of 2.94 — the rear wheel turns 2.94 times per pedal stroke. Higher ratios mean more speed per pedal revolution but require more force.
What is cadence and why does it matter for gearing?
Cadence is the number of pedal revolutions per minute (RPM). Most experienced cyclists pedal at 80-100 RPM for sustained efficiency. Matching your gear ratio to your preferred cadence at your target speed helps you ride more efficiently. Spinning in a lower gear is easier on joints than grinding a harder gear at low cadence.
What is the difference between 700c, 29, 27.5, and 26 inch wheels?
700c road wheels have a 622mm bead diameter and are standard on road bikes. 29-inch MTB wheels (also 622mm) have the same rim diameter as 700c but wider, taller tires. 27.5" (650b) wheels are 584mm — common on trail and enduro bikes. 26" wheels (559mm) are an older MTB standard. Larger wheels roll over obstacles better but add weight.
What chainring and cog combination is good for climbing?
A smaller ratio (fewer chainring teeth or more cog teeth) is easier to climb. MTB single-chainring setups often use a 30-32t chainring with a 10-50t or 10-52t cassette. Road climbing gears like 34t chainring with 32t cog give a ratio of 1.06 — you can pedal at 90 RPM and only go about 10-11 mph, which is useful for sustained steep climbs.
What gear ratio should I use for flat roads vs hills?
For flat roads at 20 mph (32 km/h), a 50t × 17t combo at 90 RPM works well. For hills, dropping to smaller chainrings (34t or 36t) or bigger cogs (28-34t) keeps cadence high without excessive effort. Most modern road bikes have compact cranksets (50/34t) with an 11-32t or 11-34t cassette to cover both scenarios.