Bicycle Gear Calculator

A bicycle gear calculator is an essential tool for cyclists who want to understand exactly how their drivetrain performs across different gear combinations. Whether you are a road cyclist optimizing for a sprint finish, a mountain biker choosing the right setup for a steep climb, or a commuter trying to maintain a comfortable cadence, knowing your gear ratios, speed, and development numbers takes the guesswork out of bike setup and training.

This calculator takes five real inputs — chainring teeth (front), cassette teeth (rear), wheel diameter (rim bead seat diameter in mm), tire width (mm), and cadence (pedaling revolutions per minute) — and computes your gear ratio, riding speed, gear inches, and development (distance traveled per crank revolution). It also generates a full gear chart showing speed across dozens of common chainring and cassette pairings at your chosen cadence.

Understanding these numbers lets you make smarter decisions when purchasing a cassette, selecting chainrings for a new build, or planning a race strategy. A cyclist who knows their gear ratios can predict exactly how fast they will travel at a given cadence, making pacing on long climbs or flat time trials far more precise than relying on feel alone.

This tool is equally useful for comparing drivetrains before buying components. Switching from a 50/34 compact double to a 48/31 semi-compact, for example, changes your top-end speed and climbing ability in measurable ways. Run both configurations through the bicycle gear calculator before spending money to confirm the upgrade suits your riding terrain and goals.

The core of every bicycle gear calculation starts with the gear ratio — the number of times the rear wheel rotates for each full crank revolution. Once you have the gear ratio, every other metric flows directly from it.

The wheel circumference accounts for both the rim diameter and the tire width. Because the tire adds material on both sides of the rim, the effective rolling diameter equals the rim bead seat diameter plus two times the tire width. Dividing by 1,000 converts millimetres to metres for speed calculations.

Speed is the product of how far you travel per crank revolution multiplied by how many revolutions you complete per minute, scaled to kilometres per hour. Gear inches is a traditional British measurement expressing the equivalent diameter of a penny-farthing wheel that would produce the same distance per crank revolution — still widely used because it gives an intuitive sense of how "hard" or "easy" a gear feels. Development is simply the distance in centimetres the bike travels for one full pedal stroke, making it the most practical metric for comparing gears across different wheel sizes.

Gear ratios determine how much distance you cover with each pedal stroke and, critically, how much effort that stroke requires. A high gear ratio (large chainring, small cassette cog) produces a long development and high speed but requires significant muscular force — ideal for flat roads and descents. A low gear ratio (small chainring, large cassette cog) produces a short development but lets you maintain a comfortable cadence on steep climbs without excessive strain on your knees and muscles.

For road cycling, a 50/11 combination on a 700c wheel with 25mm tires produces a gear ratio of 4.55, gear inches of 134.6", and a top speed of around 73 km/h at 100 RPM — reserved for all-out sprints. At the other end of the road spectrum, a 34/34 combination gives a 1.0 ratio and just 31.4" of gear inches, allowing riders to tackle climbs exceeding 20% gradient while maintaining a smooth cadence.

Mountain bike geometry introduces wider tires and smaller effective diameters, which naturally reduce speed at any given ratio. A 32/32 MTB configuration on a 29" wheel with 50mm tires still delivers a manageable climbing gear while the large wheel diameter offsets some of the speed penalty. Gravel riders often choose mid-range setups — 42/11 to 42/34 — that balance speed on packed gravel with enough low gearing for steep unpaved climbs.

When choosing a drivetrain, cyclists should first identify their target cadence (most trained cyclists aim for 85–100 RPM on flat terrain, dropping to 60–75 RPM on steep climbs) and then select chainring and cassette combinations that produce appropriate speeds and developments for their typical terrain. This bicycle gear calculator makes that comparison instant and precise.

Gear inches is a legacy measurement from the era of penny-farthing bicycles. It represents the diameter (in inches) of the driving wheel that would deliver the same mechanical advantage as your current gearing. A gear inch value of 100" means your drivetrain is equivalent to pedaling a penny-farthing with a 100-inch front wheel. While the metric might seem archaic, experienced cyclists and component manufacturers still use it because it provides a quick, intuitive comparison across different wheel sizes without needing to know cadence.

A typical road double chainset offers gear inches ranging from roughly 30" (34T chainring, 32T cassette, 700c wheel) to over 130" (53T chainring, 11T cassette). A compact double narrows this to about 30"–109". Track bikes typically operate in the 80"–100" range. MTB 1× drivetrains with a wide-range 10-51 cassette can span from approximately 17" to 83".

Development (also called "rollout" or "metres of development") is the metric equivalent and arguably more intuitive: it tells you directly how many metres or centimetres the bicycle travels per crank revolution. A development of 7.0 m means every pedal stroke moves you seven metres forward. At 90 RPM, that translates to 630 metres per minute or 37.8 km/h. Development is wheel-size neutral, making it the best metric for comparing gears across road, gravel, and mountain bike setups.

Both metrics are displayed by this bicycle gear calculator, so you can cross-reference them with published component specifications, training plans, and gearing tables used by coaches and professional teams.

Cadence — the number of crank revolutions per minute — is the other half of the speed equation. At any given speed, a higher cadence means a lower gear (easier to push), and a lower cadence means a higher gear (harder to push). Research and elite coaching practice consistently show that most trained cyclists perform best at cadences between 85 and 100 RPM for sustained efforts, as higher cadences shift effort away from slow-twitch muscle fibers toward cardiovascular output, reducing muscle fatigue on long rides.

Novice cyclists often naturally gravitate toward lower cadences (60–75 RPM) because pushing a bigger gear feels intuitively more powerful. Over time, training with this bicycle gear calculator to target specific speeds at higher cadences leads to better efficiency and reduced injury risk, particularly for the knees.

For climbing, selecting a gear that allows you to maintain at least 70 RPM up a sustained gradient prevents premature muscle exhaustion. For sprinting, elite track cyclists can reach 160–180 RPM in a gear of around 90–100 gear inches — entering those numbers into the calculator shows speeds exceeding 70 km/h. For time trialling, a cadence of 90–95 RPM in a gear producing 8–9 metres of development is a common target for club-level athletes.

The gear chart generated by this calculator shows speeds across all common chainring and cassette combinations at your chosen cadence, letting you identify which gears produce your target speed range and which represent wasteful crossover combinations best avoided (e.g. big chainring paired with large cassette cog, or small chainring with small cog — both create unnecessary chain angle and wear).