Bike Gear Calculator
Enter your chainring size, rear sprocket size, wheel size, and crank length to get your gear ratio, gear inches, meters of development per pedal stroke, gain ratio, and your speed at 60, 80, 90, and 100 rpm. Results update instantly as you type. Works for road, gravel, mountain, and single-speed bikes.
What the four gear metrics mean
Gear ratio is the simplest measure: it is just the chainring teeth divided by the rear sprocket teeth, telling you how many times the wheel rotates for each complete turn of the pedals. A ratio of 3.0 means three wheel rotations per pedal stroke. Gear inches translate that ratio into the diameter (in inches) of the equivalent penny-farthing wheel - the old fixed-wheel bicycle that had no gearing and whose large front wheel directly set the travel distance. Gear inches = wheel diameter x gear ratio, so a 700c x 25mm wheel (about 26.5 in diameter) in a 50x17 gear gives roughly 78 gear inches. Meters of development (also called rollout) is the most practical measurement: it is the distance the bike physically travels forward per pedal stroke - wheel circumference times gear ratio. At 78 gear inches your bike travels about 6.3 m per revolution. Gain ratio, introduced by Sheldon Brown, extends development by accounting for crank length: it divides the development by the circumference of the circle your foot travels. A gain ratio of 5.8 means the bike moves 5.8 times farther than your foot does, regardless of wheel size or units, making it the most consistent comparison across very different bikes.
How to use this calculator for your bike
To find your current gear, enter the front chainring and rear sprocket you are actually using, then select the wheel and tire size closest to yours. The crank arm length is printed on the crank arm, near the pedal thread, and is most commonly 170, 172.5, or 175 mm on adult bikes. The custom cadence field lets you enter your typical pedaling speed in rpm if you know it; the default 90 rpm is a common road-cycling target. To compare gears, run the calculator twice - once for your hardest gear (large chainring, smallest sprocket) and once for your easiest (smallest chainring, largest sprocket). The ratio between those two development figures is your gear range. A range of 400-500% means your hardest gear is four to five times your easiest, which is typical for a modern road compact or gravel drivetrain.
Gear ratio vs gear inches: which should you use?
Gear ratio is useful when comparing bikes with the same wheel size because the ratio directly scales travel. Gear inches are the traditional standard in English-speaking countries and still dominate discussions among road cyclists. Meters of development is preferred in continental Europe and by touring and track cyclists because it gives a concrete real-world distance. For comparing bikes with different wheel sizes (say a 26-inch MTB against a 29er) only development or gain ratio give a fair comparison, because raw gear ratio ignores the fact that a larger wheel rolls farther per revolution. Two bikes with the same chainring/sprocket ratio but different wheel sizes will have the same gear ratio but different gear inches and different development.
Cadence, speed, and selecting the right gear
Speed is development multiplied by cadence, converted to the right units. At 90 rpm in a 78-gear-inch road gear (about 6.3 m development) you travel roughly 34 km/h. Most road cyclists target 80-100 rpm because that range produces efficient muscle recruitment and keeps cardiovascular load manageable. At lower cadences you push harder per stroke, which increases muscle fatigue. At very high cadences (above 110 rpm) the technique required to stay smooth becomes demanding. Mountain bikers on technical trails often work at 60-80 rpm because the terrain controls their speed more than their gear selection. For commuters and recreational riders, 70-85 rpm is a good range to aim for. The speed-vs-cadence chart in this calculator shows you the full sweep for your current gear so you can see instantly what cadence you need to hit a target speed.
Common gear ranges by bike type
| Bike type | Typical gear inches | Low end use |
|---|---|---|
| Road racing (standard) | 70 - 110 in | Flat and fast |
| Road endurance (compact) | 35 - 95 in | Rolling terrain |
| Gravel / adventure | 28 - 85 in | Mixed surfaces |
| Cross-country MTB | 22 - 80 in | Varied climbs |
| Trail / enduro MTB | 18 - 70 in | Steep technical |
| Touring / loaded bikepacking | 20 - 80 in | Long days with load |
| Single-speed urban | 55 - 75 in | Flat city riding |
Approximate gear-inch ranges used by different bike disciplines. Actual setups vary widely.
Frequently asked questions
What is a good gear ratio for a beginner cyclist?
For flat to rolling terrain a gear ratio between 2.5 and 3.5 (roughly 55-75 gear inches on a 700c wheel) is comfortable for most beginners. For climbing, you want a gear ratio below 2.0 (under 45 gear inches) so you can maintain a reasonable cadence without grinding. A compact road crankset (50/34T) with an 11-32T cassette gives a low gear of about 28 gear inches and a high gear of about 120 gear inches, covering almost anything a beginner will encounter.
What is the difference between gear ratio and gear inches?
Gear ratio is a pure ratio - chainring teeth divided by sprocket teeth - that tells you how many times the rear wheel rotates per pedal revolution. Gear inches scales that ratio by the wheel diameter (in inches) to give the equivalent penny-farthing wheel size. Two bikes with different wheel sizes (say 26 inch and 29 inch) can have the same gear ratio but very different gear inches and very different actual speeds, because the larger wheel rolls farther per revolution.
How does crank length affect gearing?
Crank length does not affect gear ratio, gear inches, or meters of development - those depend only on chainring, sprocket, and wheel. However, crank length does affect gain ratio, because it sets the radius of the circle your foot travels. A longer crank creates a larger foot circle, so for the same travel per stroke your foot works through a larger arc. Shorter cranks are increasingly recommended for riders with hip or knee issues because the reduced arc eases joint stress at the top of the pedal stroke.
What is meters of development and why do cyclists use it?
Meters of development (also called rollout or metric development) is the distance your bike travels forward for every complete revolution of the pedals. It equals the wheel circumference multiplied by the gear ratio. It is more practical than gear inches for real-world training because it directly answers the question "how far do I move per stroke?" and it works the same way regardless of wheel size. Continental European coaches and track cyclists have historically preferred it, and it is increasingly used internationally as wheel sizes on bikes diversify.
How do I calculate my speed from gear ratio?
Multiply the meters of development by your cadence in revolutions per minute to get meters per minute, then multiply by 60 to get meters per hour, then divide by 1000 for km/h. Speed (km/h) = development (m) x cadence (rpm) x 60 / 1000. To convert to mph, multiply by 0.6214. For example, 6.0 m development at 90 rpm gives 6.0 x 90 x 60 / 1000 = 32.4 km/h, or about 20.1 mph.
What wheel size should I enter for 700c tires?
The standard 700c rim has an ETRTO inner diameter of 622 mm. The effective rolling diameter - which this calculator uses - adds the inflated tire width twice. A 700c x 25mm tire rolls on a diameter of roughly 673 mm (26.5 in), while a 700c x 28mm is about 678 mm. Choose the width closest to your actual tire. If you use a tubeless setup or a tire that runs wide, pick the next larger size to stay accurate.