Bike Gear Ratio Calculator
Work out gear inches and your speed at a given cadence for any chainring, cog, and wheel size combination.
| Chainring | Cog | Gear inches |
|---|---|---|
| 50 | 11 | 121.8 |
| 50 | 32 | 41.9 |
| 34 | 11 | 82.8 |
| 34 | 32 | 28.5 |
These four rows are the extremes of a compact road setup (50/34 chainrings, 11-32 cassette) on the wheel you picked above, from the smallest climbing gear to the biggest gear for flat ground and descents.
How it works
Gear inches describe how far your bike moves for one full turn of the pedals, expressed as the diameter, in inches, of the wheel an old-fashioned penny-farthing would need to give the same distance per pedal stroke. It's a way to compare gears across bikes with different chainrings, cogs, and wheel sizes on one common scale. The calculator takes your chainring teeth divided by your cog teeth, multiplied by your wheel's actual rolling diameter (not its nominal size, since tire width and inflation change the real number a little).
Worked example: a 50-tooth chainring, an 11-tooth cog, and a 700c road wheel at 26.8 inches of rolling diameter. That's 50 ÷ 11 × 26.8 = 121.8 gear inches, a big gear for flat roads and descents. Pedal that gear at 90 rpm and you're moving at roughly 32.6 mph. Drop to a 34-tooth chainring and a 32-tooth cog on the same wheel and you get 28.5 gear inches, a low climbing gear that at 90 rpm works out to about 7.6 mph, plenty slow enough to spin up a steep grade without grinding.
FAQ
What counts as a high gear versus a low gear?
Anything above roughly 100 gear inches is a big gear, good for fast flat riding or descending, and mostly too hard to push uphill without standing and mashing. Anything under about 30 gear inches is a winch gear, meant for grinding up a steep climb at a sustainable cadence rather than covering ground fast. Most of your riding happens somewhere in between, and a wide gear range just means you have both ends covered.
Why does cadence matter if the gear inches stay the same?
Gear inches only tell you how far one pedal stroke moves you, not how fast you're actually going, that depends on how quickly you're turning the pedals. Around 90 rpm is a common target for efficient riding because it spreads the pedaling effort across more, lighter strokes instead of fewer, harder ones, which tends to be easier on your knees and lets you ride longer before your legs fatigue.
Why does wheel size change the gear inches so much?
A bigger wheel covers more ground per rotation for the exact same chainring and cog, so a 29er wheel produces a noticeably higher gear inch number than a 26 inch mountain wheel with identical gearing. That's why comparing gear setups across different wheel sizes only makes sense in gear inches, comparing raw chainring and cog numbers alone isn't enough.
Is a compact 50/34 crankset enough for a beginner?
For most new riders, yes. Paired with an 11-32 cassette it covers a wide enough range to climb reasonably steep hills in the smaller chainring and still hold a fast pace on flats in the bigger one, without needing a triple chainring or a specialized gravel-specific setup.
For more on putting the right gear to use, see how to shift gears without the crunch, fine-tuning your gears, and how to climb hills without burning out.