Bike gear ratio calculator

A gear ratio is chainring teeth divided by cog teeth: 50 × 17 is 2.94, which on a 700 × 28 wheel moves the bike 6.26 m per pedal turn and gives 33.8 km/h at 90 rpm. Enter your chainrings, cassette and wheel size to see every gear, your speed at any cadence and where the gaps are.

Calculator

Chainrings

Comma separated, up to 3 rings.

Cassette

Wheel

Tyre width

Cadence

rpm

Cog	50	34
11
12
13
14
15
16
17
19
21
24
27
30

50 × 17: ratio 2.94, 78.5 gear inches, 6.26 m per pedal turn, 33.8 km/h at 90 rpm.

Easiest gear: 34 × 30, ratio 1.13. Hardest: 50 × 11, ratio 4.55. Range 401 %.

Ratio = chainring ÷ cog. Wheel circumference ≈ π × (rim bead seat diameter + 2 × tyre width). Speed = development × cadence × 60 ÷ 1,000.

How bike gear ratios work

A gear ratio is how many times the rear wheel turns for each turn of the pedals: chainring teeth divided by cog teeth. A bigger ratio is a harder gear, with more distance per pedal stroke and more force needed. This calculator, one of the free LeCoach cycling calculators, gives four numbers for every chainring and cog:

Ratio = chainring ÷ cog
Development = ratio × wheel circumference: distance per pedal turn
Gear inches = ratio × wheel diameter in inches, to compare gears across wheel sizes
Speed = development × cadence × 60 ÷ 1,000, in km/h

Wheel circumference is estimated as π × (rim bead seat diameter + 2 × tyre width). For a 700c wheel (622 mm bead seat) with 28 mm tyres, that is π × 678 = 2,130 mm.

Worked example. You ride a 50/34 compact chainset with an 11-30 12-speed cassette on 700 × 28 mm tyres. In 50 × 17, the ratio is 50 ÷ 17 = 2.94. Development is 2.94 × 2.13 = 6.26 m per pedal turn, which is 78.5 gear inches. At 90 rpm that gives 6.26 × 90 × 60 ÷ 1,000 = 33.8 km/h (21.0 mph). Your easiest gear, 34 × 30, has a ratio of 1.13; your hardest, 50 × 11, has 4.55. That is a range of about 400 %.

Every gear on a 50/34 with 11-30

700 × 28 mm tyres at 90 rpm.

Cog	50: ratio	50: km/h	50: gear in	34: ratio	34: km/h	34: gear in
11	4.55	52.3	121.3	3.09	35.6	82.5
12	4.17	47.9	111.2	2.83	32.6	75.6
13	3.85	44.2	102.7	2.62	30.1	69.8
14	3.57	41.1	95.3	2.43	27.9	64.8
15	3.33	38.3	89.0	2.27	26.1	60.5
16	3.13	35.9	83.4	2.13	24.4	56.7
17	2.94	33.8	78.5	2.00	23.0	53.4
19	2.63	30.3	70.2	1.79	20.6	47.8
21	2.38	27.4	63.6	1.62	18.6	43.2
24	2.08	24.0	55.6	1.42	16.3	37.8
27	1.85	21.3	49.4	1.26	14.5	33.6
30	1.67	19.2	44.5	1.13	13.0	30.3

Note the overlap: 34 × 11 (3.09) is almost the same gear as 50 × 16 (3.13), and most doubles repeat several gears. Note the jumps too: from 11 to 17 each step is 6 to 9 %, from 17 to 30 it is 10 to 14 %. That is where you feel gaps on rolling roads.

Comparing common setups

Easiest gear at 70 rpm, hardest at 90 rpm, on 700 × 28 mm unless shown.

Setup	Easiest gear (ratio)	km/h at 70 rpm	Hardest gear (ratio)	km/h at 90 rpm	Range
53/39, 11-28	39 × 28 (1.39)	12.5	53 × 11 (4.82)	55.4	346 %
52/36, 11-30	36 × 30 (1.20)	10.7	52 × 11 (4.73)	54.4	394 %
50/34, 11-30	34 × 30 (1.13)	10.1	50 × 11 (4.55)	52.3	401 %
50/34, 11-34	34 × 34 (1.00)	8.9	50 × 11 (4.55)	52.3	455 %
48/31, 10-36	31 × 36 (0.86)	7.7	48 × 10 (4.80)	55.2	557 %
40 (1x), 10-44, 700 × 40	40 × 44 (0.91)	8.4	40 × 10 (4.00)	47.6	440 %
32 (1x), 10-52, 29 × 2.4	32 × 52 (0.62)	6.0	32 × 10 (3.20)	40.4	520 %

A 48/31 with 10-36 has a lower easiest gear than a 50/34 with 11-34 and almost the top gear of a 53/39. Single-ring (1x) setups trade top speed and small steps for simplicity.

Want this worked out for you every day? LeCoach builds your training around your own numbers.

Try LeCoach for free

Choosing gearing for climbs and for speed

Start with the hardest climb you will ride. Work out your speed on it with the cycling climb calculator, then check that your easiest gear lets you hold that speed at a cadence you can sustain, typically 70 rpm or more. If you climb slower than your easiest gear gives at 70 rpm, you will grind at a low cadence, which tires your legs faster.

At the top end, 50 × 11 at 100 rpm is already 58.1 km/h, enough for most riders outside fast descents and sprints. The cycling speed calculator shows what speed your power gives on the flat; this page shows which gear that is.

If climbs are your limiter, the climbing training plan covers the fitness side.

Common mistakes

Gearing for your best day. Pick it for the last climb of a long day.
Comparing ratios across wheel sizes. Use gear inches or development instead. A 650b wheel with 47 mm tyres has the same circumference as 700 × 28 mm.
Cross-chaining. Big ring with the largest cogs, or small ring with the smallest, wears the drivetrain faster, and a straighter gear usually gives the same ratio.
Thinking a bigger top gear makes you faster. Speed comes from power; a bigger gear only helps if you spin out the one you have.

When your gearing changes

New cassette or chainrings: re-enter them and recheck your easiest gear.
Worn parts: see when to replace your cassette and when to replace your bike chain.

Ask LeCoach which gearing suits your next event and it answers from your power data and FTP.

Sources

Brown S. Gear theory for bicyclists. sheldonbrown.com.
ETRTO and ISO 5775 bead seat diameters: 622 mm (700c and 29 inch), 584 mm (650b and 27.5 inch), 559 mm (26 inch).

Frequently asked questions

How do you calculate a bike gear ratio?

Divide the chainring teeth by the rear cog teeth. A 50-tooth chainring with a 17-tooth cog is 50 ÷ 17 = 2.94, so the rear wheel turns 2.94 times per pedal turn. On a 700 × 28 mm wheel, that moves the bike 6.26 m per turn.

What are gear inches?

Gear inches are the gear ratio multiplied by the wheel diameter in inches. They come from the days of penny-farthings: a gear of 78.5 inches feels like riding a direct-drive wheel 78.5 inches across. They let you compare bikes with different wheels.

How fast will I go in a gear at a given cadence?

Speed in km/h is development in metres × cadence × 60 ÷ 1,000. In 50 × 17 on 700 × 28 mm tyres, development is 6.26 m, so at 90 rpm you ride 33.8 km/h. At 100 rpm it is 37.6 km/h.

What is a good climbing gear for a road bike?

One that lets you hold about 70 rpm or more on your hardest climb at the speed you can sustain. On a 50/34 with an 11-34 cassette, the easiest gear is a 1.00 ratio, which gives 8.9 km/h at 70 rpm. If you climb slower than your easiest gear allows, choose a lower ratio.

Is a 50/34 compact or 52/36 better?

A 50/34 compact is easier on climbs: with an 11-30 cassette, its easiest gear gives 10.1 km/h at 70 rpm against 10.7 km/h on a 52/36. The 52/36 has a slightly harder top gear, 54.4 against 52.3 km/h at 90 rpm. For hilly riding most riders are better served by the compact.

What does gear range mean?

Gear range is your hardest gear's ratio divided by your easiest, as a percentage. A 50/34 with an 11-30 cassette runs from 1.13 to 4.55, about 400 %. A 32-tooth 1x MTB setup with a 10-52 cassette reaches 520 %. Wider ranges usually mean bigger jumps.