Calculate gear ratios, gear inches, development, and speed for any bicycle drivetrain. Compare gears across cassettes and chainrings.
Choosing gearing is mostly about matching the bike to the terrain and cadence range you want to ride. Whether you are comparing a new drivetrain or checking the gears you already have, it helps to see the ratios in one place.
Bicycle gearing is often expressed as gear ratio, gear inches, or development. Each metric describes the same basic relationship in a slightly different way, which makes it easier to compare setups across wheel sizes and drivetrain styles.
This calculator generates a gear chart for a drivetrain combination so you can inspect overlaps, gaps, and the practical speed range of the setup.
A gear calculator helps you compare different drivetrains before buying and understand the practical speed range of your bike. It is useful for checking whether a cassette or chainring change will give you the climbing gears or top-end range you need.
Gear Ratio = Front Teeth / Rear Teeth. Gear Inches = Gear Ratio × Wheel Diameter (inches). Development (m) = Gear Ratio × Wheel Circumference (m). Speed (km/h) = Development × Cadence × 60 / 1000.
Result: Range: 1.00 to 4.55 (455% range)
A 50/34 compact crankset with an 11-34T cassette on 700×25c wheels provides 22 gear combinations with ratios from 1.00 (34/34, good for steep climbs) to 4.55 (50/11, for fast descents). At 85 RPM, speeds range from 10.7 km/h to 48.7 km/h.
Cyclists use gear ratio, gear inches, and development to describe drivetrain gearing. Each number tells the same basic story in a different unit.
Wider cassettes make steep climbs easier but leave larger jumps between gears. Tighter cassettes give finer cadence control on flatter terrain.
When you compare setups, start with the steepest climb and the fastest downhill or tailwind section you want to handle. That usually tells you more than chasing one ideal ratio.
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The calculator uses standard drivetrain geometry: chainring teeth divided by cog teeth, adjusted by wheel size to produce gear ratio, gear inches, and development. It is a planning aid for comparing setups, not a performance prediction.
Most road cyclists need a range of 400-600%. A compact crankset (50/34) with an 11-32 cassette gives about 480%, which suits varied terrain.
Gear inches represent the equivalent wheel diameter of a direct-drive bicycle. A 70-gear-inch setup means each pedal revolution covers the same distance as a 70-inch wheel rolling once.
A 2× drivetrain typically has overlap between chainrings. That is not wasted, because overlap often gives smoother cadence steps in the most-used speed range.
Standard (53/39) suits flatter terrain and racing. Compact (50/34) is better for climbing and general riding. Semi-compact (52/36) splits the difference.
A 1× drivetrain uses a single front chainring. It is simpler and lighter but has a narrower gear range or bigger jumps between gears.
If your cadence drops below about 60 RPM on climbs you regularly ride, you may benefit from lower gearing.