Bike Gear Ratio Calculator
Enter your chainring, cog, wheel size, and crank length to see your gear ratio, gear inches, gain ratio, development, and speed at any cadence — all four metrics cyclists actually use, in one place.
Why one gear "number" isn't enough
Ask three cyclists what gear ratio means and you'll likely get three different answers, because cycling actually uses four related but distinct metrics, and mixing them up is one of the most common points of confusion in bike mechanics. Gear ratio alone tells you how many times your rear wheel spins per pedal stroke, but it ignores wheel size entirely — which makes it useless for comparing a 26-inch mountain bike to a 700c road bike. This calculator gives you all four numbers cyclists actually rely on, computed together from the same inputs, so you're never stuck converting between them by hand.
Gear ratio, gear inches, development, and gain ratio — what each one means
Gear Ratio
Gear Ratio = Chainring Teeth ÷ Cog Teeth
The simplest metric. A 50/25 combo gives a ratio of 2.0 — the rear wheel turns twice per pedal stroke. It ignores wheel size completely, so it can't be compared across different bikes on its own.
Gear Inches
Gear Inches = Gear Ratio × Wheel Diameter (in)
Expresses your gearing as the diameter of an equivalent direct-drive penny-farthing wheel. Because it factors in wheel size, it lets you compare a mountain bike directly against a road bike. Typical road gears run from about 30 (easy climbing) to 120+ (sprinting).
Development (Rollout)
Development = Gear Ratio × Wheel Circumference
The actual distance your bike travels for one complete pedal revolution, usually expressed in meters. This is the most physically intuitive number — a 7-meter development means every full pedal stroke moves you 7 meters down the road.
Gain Ratio
Gain Ratio = (Wheel Radius ÷ Crank Length) × Gear Ratio
Devised by mechanic Sheldon Brown, this is the only metric that also accounts for crank length — longer cranks give more leverage, making an identical gear ratio feel easier. It's a pure, dimensionless number, typically between 2 and 10, making it the most complete way to compare gear "feel" across different bikes.
Two bikes can share the exact same gear inches but feel noticeably different to pedal if their crank lengths differ — a longer crank means your foot travels a greater distance through each stroke for the same wheel rotation. Gain ratio is the only one of these four numbers built to capture that difference.
Calculating speed from gear ratio and cadence
Speed = Development × Cadence (RPM) × 60 ÷ 1000 (km/h, if development is in meters)
Multiply how far you travel per pedal stroke by how many strokes per minute, and you get your speed. A development of 7 meters at a cadence of 90 RPM works out to 7 × 90 = 630 meters per minute, or 37.8 km/h. Most road cyclists pedal most efficiently between 80 and 100 RPM, with 90 RPM commonly used as a reference cadence for comparing gears.
Worked examples
50/25, 700c wheel, 90 RPM
Gear ratio: 2.0. Wheel diameter ≈ 672mm (26.5"). Gear inches: 2.0 × 26.5 ≈ 53. Development: 2.0 × 2.11m circumference ≈ 4.22m. Speed at 90 RPM ≈ 22.8 km/h — a moderate, sustainable cruising gear.
53/11, 700c wheel, 100 RPM (sprint)
Gear ratio: 4.82. Gear inches ≈ 127.7. Development ≈ 10.17m. Speed at 100 RPM ≈ 61 km/h — squarely in sprint-finish or fast-descent territory, rarely sustained for more than short bursts.
34/32, 700c wheel, 60 RPM (steep climb)
Gear ratio: 1.06. Gear inches ≈ 28.1. Development ≈ 2.24m. Speed at 60 RPM ≈ 8 km/h — a typical low gear for grinding up a steep climb at a controlled, low cadence.
46/16, 172.5mm crank — gain ratio comparison
Gear ratio: 2.875. Gain ratio: (336mm radius ÷ 172.5mm crank) × 2.875 ≈ 5.6. A road bike with 53/19 (ratio 2.79) on a 170mm crank produces a remarkably similar gain ratio of about 5.58 — nearly identical pedaling effort despite very different-looking gear numbers.
Choosing the right gearing for your riding
| Terrain / Use | Typical Gear Ratio | Common Setup |
|---|---|---|
| Steep climbing | 1.0 – 1.5 | Compact crank + wide-range cassette |
| Rolling / hilly roads | 1.8 – 2.8 | Compact crank (50/34) |
| Flat road / general riding | 2.6 – 3.5 | Standard or compact crank |
| Racing / fast flats | 3.5 – 4.8 | Standard crank (53/39) |
| Gravel (wide range) | 0.9 – 3.6 | 1x setup (40T + 10-44 cassette) |
A compact crankset (50/34) suits most recreational and hilly-terrain riders, giving easier climbing gears without sacrificing meaningful top speed. A standard crankset (53/39) generally suits strong, fast riders who spend more time at high speed on flatter terrain. Riders in genuinely hilly regions are almost always better served by the compact option, even if it looks less impressive on paper.
More sports calculators on CalcMora
If gear math has you thinking about timing and competition more broadly, a few other tools on CalcMora cover related ground. Anyone following stage races or tournament formats might find the World Cup H2H calculator useful for working out head-to-head tiebreaker scenarios, the same way this tool works out gear-vs-gear comparisons. If you're tracking event schedules across different time zones for a race or group ride abroad, the World Cup match time converter converts kickoff times the way this calculator converts gear inches — translating one unit system into another so the numbers actually make sense to you. And if baseball is more your speed once you're off the bike, the baseball WHIP calculator applies the same kind of weighted-ratio thinking to pitching performance that gain ratio applies to gearing.
Bike gear ratio calculator — FAQ
What is a bike gear ratio and how is it calculated?
A bike gear ratio is the number of teeth on your front chainring divided by the number of teeth on your rear cog. A 50-tooth chainring paired with a 25-tooth cog gives a gear ratio of 2.0, meaning the rear wheel turns twice for every single full revolution of the pedals. A higher ratio means a harder, faster gear; a lower ratio means an easier gear for climbing.
What's the difference between gear ratio, gear inches, gain ratio, and development?
Gear ratio alone ignores wheel size, so it can't be compared across bikes with different wheels. Gear inches multiplies gear ratio by wheel diameter, letting you compare a 26-inch mountain bike to a 700c road bike directly. Development (or rollout) multiplies gear ratio by wheel circumference to show the actual distance traveled per pedal stroke, usually in meters. Gain ratio, devised by bicycle mechanic Sheldon Brown, goes a step further by also factoring in crank length, since a longer crank gives more leverage and makes the same gear feel easier.
Why does crank length matter for gear ratio?
Crank length determines how far your foot travels through each pedal stroke. Two bikes with identical gear inches but different crank lengths won't feel the same to ride — the bike with the longer crank requires your foot to travel a greater distance for the same wheel rotation, effectively giving more leverage. Gain ratio is the only common gearing metric that accounts for this difference, which is why Sheldon Brown considered it the most complete way to compare gears across different bikes.
What is a good gear ratio for climbing versus flat road riding?
For steep climbing, a lower gear ratio between roughly 1.0 and 1.5 is common, giving an easier pedaling effort at the cost of speed. For flat road riding and racing, ratios between 2.6 and 4.5 are typical, with a 53-tooth chainring and 11-tooth cog producing a ratio near 4.8 for high-speed sprinting. Most cyclists use a wide range of gears across a single ride, shifting down for climbs and up for flats and descents.
How does wheel size affect my effective gearing?
Wheel size doesn't change your gear ratio itself, since that's purely a function of chainring and cog teeth, but it changes how far you travel per pedal revolution. A 29-inch mountain bike wheel covers noticeably more ground per rotation than a 26-inch wheel at the identical gear ratio. This is exactly why gear inches and development exist — they let you compare the real-world effect of a gear across different wheel sizes, which a raw gear ratio number can't do on its own.
What cadence should I use to estimate my speed?
Most road cyclists pedal most efficiently between 80 and 100 RPM, with 90 RPM commonly used as a default reference cadence. Mountain bikers and gravel riders on technical terrain often run lower, more variable cadences. Entering your typical cadence into a gear calculator gives a more personally accurate speed estimate than relying on a generic default.
Should I choose a compact or standard crankset?
A compact crankset, typically 50/34 teeth, gives easier climbing gears while still providing enough top-end gear inches for most descents and flats, which is why it suits the majority of recreational and hilly-terrain riders. A standard crankset, typically 53/39, favors strong, fast riders who spend more time at high speed on flatter terrain. Riders in hilly regions are almost always better served by a compact setup.
This tool is for educational purposes only. Always verify important results with a qualified professional.
