βοΈ Bike Gear Calculator
Gear inches, ratios, and speed for any drivetrain.
Your Gear
How to Use This Bike Gear Calculator
Thinking about a bigger chainring, a wider cassette, or just wondering what gear you are actually in? Enter the tooth counts and wheel size and this calculator returns the four numbers that describe any gear: the ratio, gear inches, development in meters, and the speed it produces at your cadence. Compare setups side by side before spending money on parts.
Enter the front chainring teeth and the rear cog teeth for the gear you want to analyze.
Enter wheel diameter in inches: 27 for 700c road wheels, 26 or 29 for mountain bikes, 20 for folding bikes.
Enter your typical cadence to see the speed that gear produces, or leave it to compare gears alone.
Change the cog or chainring and watch the numbers move: that is exactly what the new part would do on the road.
Gear Inches, Ratio, and Development Explained
Gear ratio is the raw mechanical advantage: 50/16 = 3.13 means the wheel turns 3.13 times per crank revolution. Gear inches multiply that by wheel diameter, giving the classic number cyclists have quoted for a century: 84.4 inches here. Development converts it to meters traveled per pedal stroke, 6.73 m, which is the most intuitive of the three because it directly predicts speed at any cadence.
Worked Example: 50x16 on 700c
Ratio = 50/16 = 3.13. Gear inches = 3.13 x 27 = 84.4. Development = 84.4 x 0.0254 x 3.1416 = 6.73 m per revolution. At 90 RPM that is 36.4 km/h (22.6 mph). A climbing gear like 34x28 gives 32.8 gear inches and 2.62 m development, less than half the distance per stroke, which is exactly why it feels so much easier uphill. Enter both above to compare.
Choosing Gears for Your Riding
Road bikes with compact 50/34 chainrings and 11-32 cassettes cover roughly 28 to 120 gear inches, enough for most riders from steep climbs to fast descents. If your lowest gear still has you grinding below 60 RPM on local hills, the calculator shows how much easier a 34-tooth cog would feel versus a 32: the gear inches drop proportionally, and so does the force your knees must produce. For flat-land riders, tighter cassettes matter more than wide ones, because small jumps between gears let you hold your ideal cadence as speed changes.
Mountain bikers think in range: a 1x12 drivetrain with a 32-tooth ring and 10-52 cassette spans about 16 to 86 gear inches, a huge range from a single ring. Compare your current lowest gear to the steepest climb you ride; if the numbers say you need 70 RPM at your climbing speed and your legs say otherwise, gear down. The calculator removes the guesswork from a simple question: can this gear produce the speed I need at a cadence I can hold?
Gear Inches Across Wheel Sizes
Wheel size is why gear inches exist as a concept: they normalize gears across 26, 27.5, 29, and 700c wheels. A 32x16 on a 26-inch wheel is 52 gear inches, but the same 32x16 on a 29er is 58, noticeably harder. When comparing bikes with different wheels, always compare gear inches or development, never raw tooth counts. Two bikes with identical cassettes can feel completely different if one rolls on 26-inch wheels and the other on 29.
Reading a Gear Chart Like a Mechanic
Run every combination of your drivetrain through the calculator and a pattern emerges: the chart of gear inches across your cassette. On a 2x11 road setup, you will see the big ring's gears overlap the small ring's middle gears, which is why experienced riders cross-chain less and shift the front less often than beginners expect. The useful question is not how many gears you have but whether the steps between them are even. A jump from 84 to 72 gear inches is a 14 percent change in effort at fixed cadence; jumps above 15 percent feel like hitting a wall, jumps under 8 percent feel silky.
This is how you shop for a cassette intelligently. Write down your current gear inches, then compute the candidate cassette's chart the same way. If the new 11-34 gives you a 30-inch low gear versus your current 34-inch, that is 12 percent easier climbing for the price of slightly bigger jumps at the top end. Riders in flat regions do the opposite trade: an 11-25 cassette keeps every jump tight for holding exact cadence in a pace line, sacrificing a low gear they never use. The calculator turns a 60-dollar part choice from a gamble into arithmetic.
One more mechanic's trick: gear inches expose worn drivetrains. If you replace a chainring with a different size, say 52 to 50 teeth, every gear drops about 4 percent in inches, and your familiar cadence-speed relationships all shift slightly. Recompute your two or three most-used gears after any ring or cassette change so your legs are not surprised on the first ride. It takes two minutes and prevents a week of feeling mysteriously slow.
Worked Example: The Gravel Bike 1x Setup
A gravel bike with a 40-tooth chainring, 11 to 42 cassette, and 700Γ40c wheels (about 27.4-inch diameter). Lowest gear: 40/42 Γ 27.4 = 26.1 gear inches. Highest: 40/11 Γ 27.4 = 99.6. Range: 99.6/26.1 = 382 percent. That low gear (26 inches) climbs loaded gravel grades at a sustainable cadence; the high gear (100 inches) pedals comfortably to about 28 mph at 90 rpm.
Compare a 2x road setup: 50/34 chainrings, 11 to 30 cassette. Low: 34/30 Γ 27 = 30.6 inches. High: 50/11 Γ 27 = 122.7. The 2x has a higher top end but a less low bottom, and the dreaded overlap: half the combinations duplicate ratios. The 1x gives up top speed most riders never use for a simpler, more usable range. For gravel and trail, the 1x math usually wins.
Why Gear Inches Beat Gear Ratios
A gear ratio (2.5:1) tells you nothing without wheel size: 2.5:1 on a 20-inch folding bike and 2.5:1 on a 29er are completely different gears. Gear inches multiply the ratio by wheel diameter, giving the effective diameter of the wheel you are "pushing": 60 gear inches feels like pedaling a 60-inch penny-farthing wheel. Same number, same feel, any bike.
This is what makes gear inches the comparison unit. Your 60-inch low gear and your friend's 60-inch low gear climb identically regardless of wheel size or drivetrain brand. Ratios are for mechanics adjusting a specific bike; gear inches are for riders comparing bikes. When someone asks "what gearing do you run," the gear-inch range is the informative answer.
1x vs. 2x Drivetrains: The Range Tradeoff
1x (single chainring) dominates mountain and gravel: no front derailleur to drop chains, simpler shifting, and modern wide-range cassettes (up to 520 percent) cover nearly everything. The cost: bigger jumps between gears, which matters on rolling road terrain where you want the perfect cadence, and a lower top end.
2x (double chainring) still rules road cycling: tight cassette spacing for holding exact cadence, and a high gear for 40-mph descents. The cost is complexity: front shifting under load, chain-drop risk, and overlapping ratios that waste half the combinations. Choose 1x for simplicity and low maintenance off-road; 2x for cadence precision on pavement. The terrain decides, not fashion.
Pro Tips for Climbing Gears
Gear for your weakest day, not your strongest. The low gear you need is the one that lets you spin 70+ rpm up your local climb when tired, loaded, or facing a headwind. A gear that works fresh on a good day strands you on a bad one. When in doubt, go one step lower than the math suggests.
Check chain length when changing cassette range: a bigger low cog needs a longer chain, and a too-short chain destroys the derailleur on the big-big combination. And learn the cross-chaining limits of your setup; 1x systems tolerate anything, but 2x riders should avoid big-big and small-small for drivetrain longevity.
Frequently Asked Questions
How do I calculate bike gear inches?
Divide chainring teeth by cog teeth and multiply by wheel diameter in inches. A 50-tooth ring with a 16-tooth cog on 27-inch wheels gives (50/16) x 27 = 84.4 gear inches. The calculator above also returns the ratio, development in meters, and speed at your cadence.
What is a good gear ratio for hills?
For steep climbing, most recreational riders want a lowest gear under 35 gear inches, like 34x28 on a road bike (32.8 inches). Stronger riders manage with 40 to 45. If you regularly grind below 60 RPM on climbs, your lowest gear is too hard regardless of fitness.
What does 11-32 cassette mean?
It means the smallest cog has 11 teeth and the largest has 32, with steps between. Paired with a 50/34 compact crankset, that spans roughly 28 to 122 gear inches on 700c wheels. Bigger large cogs mean easier climbing gears; the 11-tooth cog sets the top speed gear.
How many gears does my bike really have?
Fewer than advertised. A 2x11 drivetrain has 22 combinations but several overlap: the actual distinct gear inches might number 14 to 16. What matters is the range from lowest to highest and the step sizes between gears, both of which this calculator reveals.
What is gear development?
The distance the bike travels per crank revolution, in meters. A 50x16 on 700c wheels develops 6.73 m per stroke. It is the most practical gear number because speed equals development times cadence, so it directly answers how fast a gear goes at your pedaling rate.
Should I get a bigger chainring to go faster?
Only if you spin out your current biggest gear. If you can already hold 90-plus RPM in your top gear on descents, a bigger ring adds speed. If you rarely use the smallest two cogs, a bigger ring just moves every gear harder and hurts your climbing. Check with the calculator first.
What gear inches do pro road cyclists use?
Typically 30 to 130-plus across the whole cassette: compact lows around 34x32 (28.7 inches) for mountain stages and 54x11 or 55x11 (132-plus inches) for flat sprints and fast descents. Pros also favor tighter cassettes with small jumps between gears, so they can hold their ideal cadence precisely as race speed changes.
Do gear inches matter for e-bikes?
Less than on regular bikes, because the motor fills the gaps between gears and flattens the climbs, but they still set your comfortable cadence range and the top assisted speed. Many e-bikes use wide-range cassettes so riders can spin efficiently at 80-plus RPM while the motor handles the heavy work on steep pitches.