Calculate gear ratios, gear inches, development, and speed for any bicycle drivetrain. Compare gears across cassettes and chainrings.
Choosing the right gearing for your bicycle can make the difference between an enjoyable ride and a miserable slog. Whether you're building a new bike, upgrading your drivetrain, or simply trying to understand what gears you currently have, a gear calculator is an essential tool for every cyclist.
Bicycle gearing is expressed in several ways: gear ratio (chainring teeth divided by cog teeth), gear inches (an older standard that accounts for wheel size), and development (the distance traveled per pedal revolution in meters). Each metric tells you something different about how a gear will feel and perform. Gear inches historically compared everything to the equivalent penny-farthing wheel diameter, while development is more intuitive for metric users.
Modern road bikes typically offer gear ranges from about 2.0 to 4.8 ratio, giving roughly a 580% range with an 11-34 cassette and 50/34 compact crankset. Mountain bikes prioritize low gears for climbing, with 1× drivetrains offering ratios as low as 0.6 with a 10-52T cassette. This calculator generates a complete gear chart for any drivetrain combination, helping you visualize overlaps, gaps, and the practical speed range of your setup.
A gear calculator helps you plan drivetrain upgrades, compare different setups before buying, and understand the practical speed range of your bike. It prevents expensive mistakes like buying a cassette that doesn't provide the low gears you need. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation.
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, perfect 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 three main systems to describe gearing. The simple gear ratio (front ÷ rear) is the most common but doesn't account for wheel size. Gear inches multiply the ratio by wheel diameter, creating a standard that works across bike types. Development (meters per revolution) is the most practical — it directly tells you how far you travel with each pedal stroke. A development of 8.0m means each complete pedal revolution moves you 8 meters forward.
The cassette is the most cost-effective way to change your gearing. Modern wide-range cassettes like the Shimano 11-34T or SRAM 10-52T have transformed what's possible without changing chainrings. The trade-off with wider ranges is bigger jumps between gears, which can leave you searching for the perfect cadence on flat terrain. For pure road riding, an 11-28T cassette offers tight, evenly-spaced gears. For mixed terrain or hilly routes, 11-34T provides the climbing bailout gears you need.
When planning a bike build or upgrade, start with the extremes: what's the steepest climb you'll ride, and what's the fastest descent you need to pedal through? A 15% gradient at 6 km/h requires a gear ratio near 1.0, while pedaling at 55 km/h downhill needs a ratio of about 5.0. Most cyclists never need the very highest gears — even pros rarely spin out a 53/11 on flat terrain. Investing in lower climbing gears typically pays bigger dividends than chasing top-end speed.
Most road cyclists need a range of 400-600%. A compact crankset (50/34) with an 11-32 cassette gives about 480%, suitable for varied terrain. Hillier areas benefit from an 11-34 cassette.
Gear inches represent the equivalent wheel diameter of a direct-drive (penny-farthing) bicycle. A 70-gear-inch setup means each pedal revolution covers the same distance as a 70-inch wheel rolling once. Typical road gears range from 20 to 120 gear inches.
A 2× drivetrain typically has 30-50% overlap between chainrings. This isn't wasted — overlapping gears often provide smoother cadence steps in the most-used speed range.
Standard (53/39) suits flat terrain and racing. Compact (50/34) is better for climbing and general riding. Semi-compact (52/36) splits the difference. Your choice depends on terrain and fitness.
A 1× (pronounced "one-by") drivetrain uses a single front chainring. It's simpler and lighter but has a narrower gear range or bigger jumps between gears. Ideal for mountain biking and gravel riding.
If your cadence drops below 60 RPM on climbs you regularly ride, you need lower gearing. Either add a larger rear cog or switch to a smaller chainring.