How to calculate gear development
Development is the distance your bike travels with one full turn of the cranks. It combines the gear ratio with the wheel size, which makes it the most direct way to compare gears across different bikes.
- Formula
- Development (m) = chainring teeth ÷ cog teeth × tyre circumference (m)
- Example
- 50 × 17 with 700 × 28c (2136 mm): 50 ÷ 17 = 2.94 × 2.136 m = 6.28 m
- Speed
- Development × cadence × 60 ÷ 1000 = km/h. 6.28 m at 90 rpm gives 33.9 km/h (21.1 mph).
- Gear inches
- Gear ratio × wheel diameter in inches. 50 × 17 with 700 × 28c is 78.7 gear inches; development in metres = gear inches × π × 0.0254.
- Circumference
- Most accurate when measured: mark the tyre with the valve at the bottom, roll the bike one full revolution with your weight on it and measure the distance in mm.
Development, gear ratio, gear inches and gain ratio
The gear ratio (chainring ÷ cog) only tells you how often the rear wheel turns per crank revolution – the wheel size is missing. Development adds the tyre circumference and gives you metres. Gear inches follow the same principle, based on the wheel diameter in inches. The gain ratio also takes crank length into account.
For “Can I get up this climb?” the development of your easiest gear matters, for “Can I still pedal downhill?” the hardest one. How much power a gear costs on a climb is shown by the cycling power calculator.
Gear development charts
| Ring | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 19 | 21 | 24 | 27 | 30 | 34 | 36 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 54 | 11.53 | 10.49 | 9.61 | 8.87 | 8.24 | 7.69 | 7.21 | 6.78 | 6.07 | 5.49 | 4.81 | 4.27 | 3.84 | 3.39 | 3.20 |
| 53 | 11.32 | 10.29 | 9.43 | 8.71 | 8.09 | 7.55 | 7.08 | 6.66 | 5.96 | 5.39 | 4.72 | 4.19 | 3.77 | 3.33 | 3.14 |
| 52 | 11.11 | 10.10 | 9.26 | 8.54 | 7.93 | 7.40 | 6.94 | 6.53 | 5.85 | 5.29 | 4.63 | 4.11 | 3.70 | 3.27 | 3.09 |
| 50 | 10.68 | 9.71 | 8.90 | 8.22 | 7.63 | 7.12 | 6.68 | 6.28 | 5.62 | 5.09 | 4.45 | 3.96 | 3.56 | 3.14 | 2.97 |
| 48 | 10.25 | 9.32 | 8.54 | 7.89 | 7.32 | 6.84 | 6.41 | 6.03 | 5.40 | 4.88 | 4.27 | 3.80 | 3.42 | 3.02 | 2.85 |
| 46 | 9.83 | 8.93 | 8.19 | 7.56 | 7.02 | 6.55 | 6.14 | 5.78 | 5.17 | 4.68 | 4.09 | 3.64 | 3.28 | 2.89 | 2.73 |
| 39 | 8.33 | 7.57 | 6.94 | 6.41 | 5.95 | 5.55 | 5.21 | 4.90 | 4.38 | 3.97 | 3.47 | 3.09 | 2.78 | 2.45 | 2.31 |
| 36 | 7.69 | 6.99 | 6.41 | 5.92 | 5.49 | 5.13 | 4.81 | 4.52 | 4.05 | 3.66 | 3.20 | 2.85 | 2.56 | 2.26 | 2.14 |
| 35 | 7.48 | 6.80 | 6.23 | 5.75 | 5.34 | 4.98 | 4.67 | 4.40 | 3.93 | 3.56 | 3.12 | 2.77 | 2.49 | 2.20 | 2.08 |
| 34 | 7.26 | 6.60 | 6.05 | 5.59 | 5.19 | 4.84 | 4.54 | 4.27 | 3.82 | 3.46 | 3.03 | 2.69 | 2.42 | 2.14 | 2.02 |
| 33 | 7.05 | 6.41 | 5.87 | 5.42 | 5.03 | 4.70 | 4.41 | 4.15 | 3.71 | 3.36 | 2.94 | 2.61 | 2.35 | 2.07 | 1.96 |
| Ring | 10 | 11 | 13 | 15 | 17 | 19 | 21 | 24 | 28 | 32 | 38 | 44 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 48 | 10.56 | 9.60 | 8.12 | 7.04 | 6.21 | 5.56 | 5.03 | 4.40 | 3.77 | 3.30 | 2.78 | 2.40 |
| 46 | 10.12 | 9.20 | 7.78 | 6.75 | 5.95 | 5.33 | 4.82 | 4.22 | 3.61 | 3.16 | 2.66 | 2.30 |
| 44 | 9.68 | 8.80 | 7.45 | 6.45 | 5.69 | 5.09 | 4.61 | 4.03 | 3.46 | 3.03 | 2.55 | 2.20 |
| 42 | 9.24 | 8.40 | 7.11 | 6.16 | 5.44 | 4.86 | 4.40 | 3.85 | 3.30 | 2.89 | 2.43 | 2.10 |
| 40 | 8.80 | 8.00 | 6.77 | 5.87 | 5.18 | 4.63 | 4.19 | 3.67 | 3.14 | 2.75 | 2.32 | 2.00 |
| 38 | 8.36 | 7.60 | 6.43 | 5.57 | 4.92 | 4.40 | 3.98 | 3.48 | 2.99 | 2.61 | 2.20 | 1.90 |
| Ring | 10 | 12 | 14 | 16 | 18 | 21 | 24 | 28 | 32 | 36 | 42 | 51 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 36 | 8.37 | 6.98 | 5.98 | 5.23 | 4.65 | 3.99 | 3.49 | 2.99 | 2.62 | 2.33 | 1.99 | 1.64 |
| 34 | 7.91 | 6.59 | 5.65 | 4.94 | 4.39 | 3.77 | 3.30 | 2.82 | 2.47 | 2.20 | 1.88 | 1.55 |
| 32 | 7.44 | 6.20 | 5.32 | 4.65 | 4.14 | 3.54 | 3.10 | 2.66 | 2.33 | 2.07 | 1.77 | 1.46 |
| 30 | 6.98 | 5.82 | 4.98 | 4.36 | 3.88 | 3.32 | 2.91 | 2.49 | 2.18 | 1.94 | 1.66 | 1.37 |
| Groupset | Rings · cassette | Tyre | Easiest | Hardest | Range |
|---|---|---|---|---|---|
| Dura-Ace R9200 | 52/36 · 11-30 | 700 × 28c | 2.56 m | 10.10 m | 394 % |
| Ultegra R8100 | 52/36 · 11-34 | 700 × 28c | 2.26 m | 10.10 m | 446 % |
| 105 R7100 | 50/34 · 11-34 | 700 × 28c | 2.14 m | 9.71 m | 455 % |
| 105 R7000 | 52/36 · 11-30 | 700 × 28c | 2.56 m | 10.10 m | 394 % |
| Tiagra 4700 | 50/34 · 11-32 | 700 × 28c | 2.27 m | 9.71 m | 428 % |
| Sora R3000 | 50/34 · 11-32 | 700 × 28c | 2.27 m | 9.71 m | 428 % |
| Claris R2000 | 50/34 · 11-32 | 700 × 28c | 2.27 m | 9.71 m | 428 % |
| GRX RX820 2x | 48/31 · 11-36 | 700 × 40c | 1.89 m | 9.60 m | 507 % |
| GRX RX820 1x | 40 · 10-45 | 700 × 40c | 1.96 m | 8.80 m | 450 % |
| XT M8100 1x | 32 · 10-51 | 29″ × 2.4 | 1.46 m | 7.44 m | 510 % |
| Red AXS 2x | 50/37 · 10-28 | 700 × 28c | 2.82 m | 10.68 m | 378 % |
| Force AXS 2x | 48/35 · 10-33 | 700 × 28c | 2.27 m | 10.25 m | 453 % |
| Rival AXS 2x | 46/33 · 10-36 | 700 × 28c | 1.96 m | 9.83 m | 502 % |
| Force XPLR 1x | 40 · 10-44 | 700 × 40c | 2.00 m | 8.80 m | 440 % |
| Apex XPLR 1x | 40 · 11-44 | 700 × 40c | 2.00 m | 8.00 m | 400 % |
| GX Eagle | 32 · 10-52 | 29″ × 2.4 | 1.43 m | 7.44 m | 520 % |
| Super Record Wireless | 50/34 · 11-29 | 700 × 28c | 2.50 m | 9.71 m | 388 % |
| Record 12 | 52/36 · 11-29 | 700 × 28c | 2.65 m | 10.10 m | 381 % |
| Chorus 12 | 48/32 · 11-34 | 700 × 28c | 2.01 m | 9.32 m | 464 % |
| Ekar 13 | 40 · 10-44 | 700 × 40c | 2.00 m | 8.80 m | 440 % |
| Tyre | Circumference | 50 × 17 | 34 × 34 | 32 × 51 |
|---|---|---|---|---|
| 700 × 23c | 2096 mm | 6.16 m | 2.10 m | 1.32 m |
| 700 × 25c | 2105 mm | 6.19 m | 2.11 m | 1.32 m |
| 700 × 28c | 2136 mm | 6.28 m | 2.14 m | 1.34 m |
| 700 × 30c | 2146 mm | 6.31 m | 2.15 m | 1.35 m |
| 700 × 32c | 2155 mm | 6.34 m | 2.16 m | 1.35 m |
| 700 × 35c | 2168 mm | 6.38 m | 2.17 m | 1.36 m |
| 700 × 40c | 2200 mm | 6.47 m | 2.20 m | 1.38 m |
| 700 × 45c | 2242 mm | 6.59 m | 2.24 m | 1.41 m |
| 650b × 47 | 2120 mm | 6.24 m | 2.12 m | 1.33 m |
| 27.5″ × 2.4 | 2200 mm | 6.47 m | 2.20 m | 1.38 m |
| 29″ × 2.2 | 2288 mm | 6.73 m | 2.29 m | 1.44 m |
| 29″ × 2.4 | 2326 mm | 6.84 m | 2.33 m | 1.46 m |
Frequently asked questions about gear development
What is gear development on a bike?
Development (also called metres of development or rollout) is the distance the bike travels with one crank revolution. With 50 × 17 and a 700 × 28c tyre it is 6.28 m, in the easiest gear 34 × 34 only 2.14 m.
How do you calculate gear development?
Chainring teeth divided by cog teeth, multiplied by the tyre circumference. Example: 50 ÷ 17 × 2.136 m = 6.28 m.
What development do I need for steep climbs?
The smaller, the easier. A road bike with 34 × 34 gets 2.14 m – at 70 rpm that is 9.0 km/h (5.6 mph). Gravel bikes with 40 × 44 reach 2.00 m, an MTB with 32 × 51 and 29″ × 2.4 even 1.46 m.
What is the development of the hardest gear?
50 × 11 gives 9.71 m, 53 × 11 gives 10.29 m (700 × 28c). At 100 rpm that is 58.3 and 61.7 km/h (36.2 and 38.4 mph).
Does tyre width change development?
Yes, but only slightly: from 700 × 25c (2105 mm) to 700 × 32c (2155 mm) the circumference grows by 2.4 %. In 50 × 17 development increases from 6.19 m to 6.34 m.
What is the gear range of a drivetrain?
Gear range is the hardest gear divided by the easiest gear, in percent. A high value means plenty of room from steep climbs to fast descents. Modern 1x drivetrains with 10-52 exceed 500 %, classic road compact cranks with 11-34 reach about 450 %.
Development, gear ratio or gear inches – which should I compare?
Gear ratio is enough as long as the wheel size stays the same. Between road, gravel and MTB, development is better because it includes the tyre. Gear inches follow the same idea based on wheel diameter: 50 × 17 with 700 × 28c is 78.7 gear inches, which equals 6.28 m of development.