Bike gear range calculator
Drivetrain A covers a range of 455 % and drivetrain B 440 %. The lowest gear is 26.7 in on A and 24.3 in on B, a change of -9.1 %. The highest gear is 121.3 in on A and 106.8 in on B, a change of -12.0 %.
Result
Gear range of A
%
Gear range of B
%
Lowest gear of A, gear inches
in
Lowest gear of B, gear inches
in
Highest gear of A, gear inches
in
Highest gear of B, gear inches
in
Lowest gear, B compared with A
%
Highest gear, B compared with A
%
How it works
Gear range percent is the highest gear divided by the lowest. It needs only four numbers: the largest and smallest chainring and the largest and smallest cog. The range tells you how far apart the ends are, not where they sit, so the calculator also gives the lowest gear in gear inches and the highest, and how much each moves when you go from A to B. That is the question behind one-by versus two-by gearing: a single ring with a wide cassette can match the range of a double and still have a harder bottom gear. Use it to compare two drivetrains before you buy a cassette or a crankset. Cassette gear steps, the jumps between neighboring cogs, are not part of the range; a wider range on the same number of cogs always means bigger steps.
Formula
lowest gear = smallest chainring ÷ largest cog; highest gear = largest chainring ÷ smallest cog. Range = highest ÷ lowest, written as a percentage (a highest gear 4.28 times the lowest is a range of 428 %). Gear inches = wheel diameter in inches × ratio. Change = gear on B ÷ gear on A − 1.
Worked example
The calculator opens with this example; the result above is computed from it.
| Input | Value |
|---|---|
| A: largest chainring | 50 |
| A: smallest chainring | 34 |
| A: smallest cog | 11 |
| A: largest cog | 34 |
| B: largest chainring | 40 |
| B: smallest chainring | 40 |
| B: smallest cog | 10 |
| B: largest cog | 44 |
| Rim size | 622 = 700C, 29 inch |
| Tire width | 28 mm |
| Gear range of A | 455 % |
| Gear range of B | 440 % |
| Lowest gear of A, gear inches | 26.7 in |
| Lowest gear of B, gear inches | 24.3 in |
| Highest gear of A, gear inches | 121.3 in |
| Highest gear of B, gear inches | 106.8 in |
| Lowest gear, B compared with A | -9.1 % |
| Highest gear, B compared with A | -12.0 % |
Common cases
| Case | Starting values | Gear range of A | Gear range of B | Lowest gear of A, gear inches | Lowest gear of B, gear inches | Highest gear of A, gear inches | Highest gear of B, gear inches | Lowest gear, B compared with A | Highest gear, B compared with A |
|---|---|---|---|---|---|---|---|---|---|
| Road double against a gravel single ring | A: largest chainring 50; A: smallest chainring 34; A: smallest cog 11; A: largest cog 34; B: largest chainring 40; B: smallest chainring 40; B: smallest cog 10; B: largest cog 44; Tire width 28 mm | 455 % | 440 % | 26.7 in | 24.3 in | 121.3 in | 106.8 in | -9.1 % | -12.0 % |
| Compact against semi-compact road cranks | A: largest chainring 50; A: smallest chainring 34; A: smallest cog 11; A: largest cog 30; B: largest chainring 52; B: smallest chainring 36; B: smallest cog 11; B: largest cog 30; Tire width 28 mm | 401 % | 394 % | 30.3 in | 32.0 in | 121.3 in | 126.2 in | 5.9 % | 4.0 % |
| Two wide-range mountain bike cassettes | A: largest chainring 32; A: smallest chainring 32; A: smallest cog 11; A: largest cog 42; B: largest chainring 32; B: smallest chainring 32; B: smallest cog 10; B: largest cog 51; Tire width 60 mm | 382 % | 510 % | 22.3 in | 18.3 in | 85.0 in | 93.5 in | -17.6 % | 10.0 % |
| Touring triple against a road compact | A: largest chainring 48; A: smallest chainring 26; A: smallest cog 11; A: largest cog 34; B: largest chainring 50; B: smallest chainring 34; B: smallest cog 11; B: largest cog 34; Tire width 35 mm | 571 % | 455 % | 20.8 in | 27.2 in | 118.9 in | 123.8 in | 30.8 % | 4.2 % |
| Gravel double against a gravel single ring | A: largest chainring 46; A: smallest chainring 30; A: smallest cog 11; A: largest cog 34; B: largest chainring 42; B: smallest chainring 42; B: smallest cog 10; B: largest cog 44; Tire width 40 mm | 474 % | 440 % | 24.4 in | 26.4 in | 115.6 in | 116.1 in | 8.2 % | 0.4 % |
Questions and answers
Does a one-by drivetrain have less gear range than a two-by?
Not always. A road double with rings of 50 and 34 teeth covers 455 %; a single ring with a cassette from 10 to 44 teeth covers 440 %. The ends move, though: the lowest gear changes by -9.1 % and the highest by -12.0 %.
How much gear range does a bigger cassette add?
On the same chainring, a cassette from 11 to 42 teeth has a range of 382 % and one from 10 to 51 teeth has 510 %. The lowest gear goes from 22.3 in to 18.3 in.
Assumptions and limits
- Only the largest and smallest sprockets matter for the range. A middle chainring and the cogs in between do not change it.
- The range says nothing about the size of the steps between gears, or how many gears repeat on a double or triple.
- Both drivetrains are worked out on the same wheel. The wheel does not change the range, only the gear inches.
- Whether a rear derailleur can handle a cassette is a question for its maker's specification, not for this arithmetic.
The result is an estimate for planning, not professional advice.
Sources
- Wikipedia: Bicycle gearing (gear range as highest gear over lowest, with a table of drivetrains; gear inches)retrieved 2026-10-13
- Sheldon Brown: gear inches (wheel diameter times front teeth over rear teeth)retrieved 2026-10-13
- Wikipedia: ISO 5775 (bead seat diameters of bicycle rims)retrieved 2026-10-13
Last updated:
Method in depth: Gear range of a drivetrain
Cite this page: Crank Math, “Bike gear range calculator”, https://crank-math.pages.dev/gearing/bike-gear-range-calculator/ (updated 13 October 2026).
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