Bike Gear Ratio Calculator

How to use the calculator

1. Pick your chainrings. You will find compact, semi-compact, gravel and the most common 1x options. If yours are not listed, type them with dashes: “50-34” or “42”.
2. Pick your cassette. They are sorted by riding type and labeled with their groupset. If yours is missing, type the teeth from smallest to largest: “11-12-13-14-15-17-19-21-24-27-30-34”. The tooth count is stamped on each cog.
3. Set the wheel and rear tire width. A 700×28 and a 700×40 do not roll the same distance: the wider tire has a larger diameter.
4. Adjust the cadence you usually ride at (90 rpm is a good value on the flats) to see your speed in each gear.
5. Read the chart. You can show it in gear inches, meters, speed, gain ratio or plain ratio. Hatched cells are cross-chained combinations, and the outlined ones are your easiest and hardest gears.
6. Compare with another drivetrain and check whether it gets you up the climb: enter the grade, your weight with the bike and the watts you can hold.

Save to My bike stores your chainrings, cassette, wheel, tire and crank length for the other calculators.

Open it pre-filled

You can link to the calculator with your data already in. For example, /calculators/gear-ratio/?platos=50-34&cassette=11-34&ancho=28. Parameters:

How we calculate it

Everything comes from the gear ratio (chainring ÷ cog) and the real size of the wheel:

Gear inches = chainring ÷ cog × wheel diameter (inches)

Development (m) = chainring ÷ cog × wheel circumference (m)

Speed (km/h) = development × cadence × 60 ÷ 1,000 (divide by 1.609 for mph)

Gain ratio = (wheel radius ÷ crank length) × chainring ÷ cog

Development (also called meters of development or rollout) is the distance the bike travels with one full turn of the cranks. It is the usual measure in Europe; gear inches is the usual one in the US. Both tell you the same thing.

We calculate the circumference as π × (BSD + 2 × tire height), with the height at 97% of the width. For a 700×28 that gives 2,125 mm (83.7 in); the CatEye chart says 2,136 mm, a 0.5% difference. For the exact size of your wheel, use the tire size calculator.

We also calculate:

• Gear range: the hardest gear divided by the easiest. A 50/34 with an 11-34 has 455%: the hardest gear goes 4.55 times as far per pedal stroke as the easiest.
• Steps between cogs: how much the ratio changes from one cog to the next. Under 10% you barely notice it; over 15% you feel your cadence “drop” when you shift.
• Usable gears: the ones that are not cross-chained. On a double, we drop the big ring with the two largest cogs and the small ring with the two smallest.
• Distinct gears: the usable ones that are more than 3% apart from the previous one. On a 2x, many gears overlap between rings.

For “Can I climb it?” we estimate your speed with the cycling power model by Martin and colleagues (1998): gravity, rolling resistance and air drag, with a climbing position and normal pavement. That speed gives your cadence in the easiest gear. If it drops below 70 rpm, we tell you which cog or small chainring would keep you at 70.

We checked the teeth on every cassette one by one against the official Shimano, SRAM, Campagnolo and microSHIFT specs (links in the sources).

Reference gear chart

Gear inches, meters per pedal stroke and speed at 90 rpm. Road with 700×28, gravel with 700×40 and mountain with 29×2.4.

Every common chainring and cassette combination is in the gear development chart in meters, speeds at each cadence are in the speed by cadence chart, and there is a shop-ready sheet in the printable gear chart.

Notice two things. SRAM’s 48×10 is almost the same as the classic 53×11: smaller chainrings with a 10-tooth cog give you the same top gear with less weight. And a mountain bike climbs in gears that are almost half as hard as a road bike’s, because on dirt you ride slower and against more resistance.

1x or 2x: what really changes

A 1x drivetrain (a single chainring) gets rid of the front derailleur and the left shifter. It is lighter, simpler and rarely clogs with mud. The tradeoff: to get enough range it needs a cassette with a big gap between the smallest and largest cog, so the steps are bigger.

We ran three drivetrains through the calculator on the same 700×40 wheel:

The 1x comes up short on range: you give up either the hardest gear or the easiest one. And from cog to cog your cadence changes by almost 15% on average, versus 11% on the 2x. On the road, riding in a group at 22-25 mph (35-40 km/h), you feel that jump. On gravel roads, with constant changes of pace and mud, the 1x is worth it.

Go 1x if you ride gravel or mountain, want simplicity or ride in mud. Go 2x if you ride road, do group rides or want both a very easy gear and a very hard one.

Common mistakes

• Counting cogs only. A 2x12 does not have 24 usable gears. Look at the distinct gears and the steps.
• Comparing cassettes by the biggest cog. A 10-36 with a 35-tooth ring (25.9 in, 2.07 m) is almost the same as an 11-34 with a 34-tooth ring (26.6 in, 2.12 m). What matters is the ratio.
• Forgetting the tire. Going from 28 to 40 mm makes every gear 3.5% harder. On a mountain bike, a 29×2.4 versus a 29×2.2 changes things by about 2%.
• Choosing your easiest gear for the average grade. Choose it for the steepest pitch you will climb when you are tired, not for the average of the climb.
• Cross-chaining out of habit. Big ring with the biggest cogs works, but the chain runs at an angle, rubs, makes noise and wears out the chain and cogs faster. There is almost always an equal gear without crossing.

Changing your cassette? Check your chain length next: with a bigger largest cog, you may need more links.

Updated October 19, 2026 ·Report an error on this page