Bike Gear Ratio Calculator

This bike gear ratio calculator shows how hard a gear is to push and how fast it rides: enter the teeth at the front and rear, tire size and cadence, then read the ratio, gear inches and speed.

Example: Chainring (front teeth) 50 teeth · Cog (rear teeth) 16 teeth · Wheel and tire: Road/gravel 700 × 28C · Cadence 90 rpm · Speed in: mph → Ratio and speed: Ratio 3.13 : 1 – 6.68 m per crank turn, 22.4 mph at 90 rpm. Source: Sheldon Brown – Gain Ratios (Gear Inches = Raddurchmesser × Kettenblatt ÷ Ritzel). Updated: 1 October 2026.

Chainring (front teeth)

teeth

for example 50, or 34 on a compact crank

Cog (rear teeth)

teeth

for example 16 for a middle gear

Wheel and tire

Cadence

rpm

crank revolutions per minute, many riders use 80–100

Speed in

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Result

Ratio and speed: Ratio 3.13 : 1 – 6.68 m per crank turn, 22.4 mph at 90 rpm
All cogs with this chainring: Cog Ratio Development (m) mph
11 4.55 9.71 32.6
12 4.17 8.9 29.9
13 3.85 8.22 27.6
14 3.57 7.63 25.6
15 3.33 7.12 23.9
16 3.13 6.68 22.4
17 2.94 6.28 21.1
18 2.78 5.93 19.9
19 2.63 5.62 18.9
21 2.38 5.09 17.1
23 2.17 4.64 15.6
25 2 4.27 14.3
28 1.79 3.81 12.8
32 1.56 3.34 11.2
36 1.39 2.97 10
Details: Gear inches: 83.7 (ratio × wheel diameter in inches).
Rolling circumference: 2,136 mm. The tire presets are typical values; tire model, pressure and load shift them by one or two percent.
Table: the same chainring with all common cogs, speed at 90 rpm.; Calculated without slip or chain angle. Real speed also depends on wind, grade and leg strength.

Cog	Ratio	Development (m)	mph
11	4.55	9.71	32.6
12	4.17	8.9	29.9
13	3.85	8.22	27.6
14	3.57	7.63	25.6
15	3.33	7.12	23.9
16	3.13	6.68	22.4
17	2.94	6.28	21.1
18	2.78	5.93	19.9
19	2.63	5.62	18.9
21	2.38	5.09	17.1
23	2.17	4.64	15.6
25	2	4.27	14.3
28	1.79	3.81	12.8
32	1.56	3.34	11.2
36	1.39	2.97	10

How it is calculated

A 50-tooth chainring with a 16-tooth cog gives a ratio of 3.13 : 1; with a 28 mm road tire the bike travels about 6.7 m per crank revolution. The calculator takes your tooth counts and shows the development and speed.

How it is calculated

The ratio is the front tooth count divided by the rear tooth count. Multiplied by the rolling circumference of the tire it gives the development: the distance per crank revolution. Multiply that by cadence and by 60 for meters per hour, which is your speed. Gear inches, the figure common in English-speaking countries, is the wheel diameter in inches times the ratio.

Which ratio fits?

Low ratio (below 2 : 1): an easy climbing gear, quick legs on steep hills.
Medium ratio (2 to 3.5 : 1): everyday riding and flat roads.
High ratio (4 : 1 and up): fast riding on the flat and downhill.

The table lists your chainring with all common cogs, so gaps in the gearing show up at once. Related tools: the chain length calculator, the speed calculator and the slope calculator.

Frequently asked questions

How do I calculate a bike gear ratio?

Divide the teeth of the chainring by the teeth of the cog. 50 ÷ 16 gives 3.13, so the wheel turns 3.13 times per crank revolution.

What is development in cycling?

The distance the bike travels per crank revolution, in meters. It equals the gear ratio times the rolling circumference of the tire.

What cadence is normal?

Many casual riders pedal 70 to 90 rpm, sporty riders often 85 to 100. Try several values, the calculator shows the matching speed.

How do I measure the rolling circumference?

Mark the tire position on the ground, roll forward one full wheel turn with your weight on the bike and measure the distance. This is often more accurate than a table.

Sources and legal basis

As of: 1 October 2026 · Editorial policy