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Gear ratio calculator
Your easiest and hardest gear, real speeds at your cadence, and every gear on one chart. Thinking about a new cassette or chainrings? Compare it with what you ride now and see exactly what changes before you spend anything.
Pedal revolutions per minute. 85–95 is typical on the flat; 70–80 is common on climbs.
Speeds are at your chosen cadence. Each gear also shows its ratio and how far the bike travels for one turn of the pedals.
Every gear, on one scale
Wheel circumference is estimated from rim size and tyre width; real tyres vary by a percent or two. For exact speeds, measure your own rollout.
How this calculator works
A gear ratio is just chainring teeth divided by sprocket teeth: 50/17 is 2.94, so the wheel turns 2.94 times for every turn of the pedals. On its own that number can't compare bikes, because a bigger wheel goes further per turn. So this calculator works out your wheel's real circumference from the rim size and tyre width, then turns every gear into three things you can actually feel: development (metres travelled per pedal turn), speed at your cadence, and gear inches for anyone who grew up with them.
Circumference is estimated as π × (rim bead seat diameter + 2 × tyre width). The bead seat diameter is the standard ISO size of the rim: 622 mm for 700c and 29", 584 mm for 650b and 27.5", 559 mm for 26". A 700 × 28 tyre comes out at about 2,130 mm, within a percent of measured rollout tables.
Will a bigger cassette help me climb?
That's the question compare mode is built for. Your easiest gear gets easier by exactly the ratio of the largest sprockets: moving from a 30 to a 34-tooth sprocket on the same chainring makes it about 12% easier, meaning roughly 12% less force on the pedals at the same climbing speed. As a rough guide, an easiest gear around 1:1 (34 × 34, say) lets most riders keep spinning on long climbs of 8–10%. If you regularly grind below 70 rpm on your local hills, you'll feel the difference of going lower.
The catch is what happens elsewhere. Wider cassettes have bigger jumps between neighbouring sprockets, which is why the summary shows the biggest step, and some need a longer derailleur cage or a different rear mech altogether. Check your derailleur's maximum sprocket size before you buy.
Reading the gear chart
Every chainring and sprocket combination is a dot on one speed scale, one row per chainring. Clusters of dots close together are near-duplicate gears; wide gaps are where you'll feel the shift. Faded dots are cross-chained: the big ring with the largest sprockets or the small ring with the smallest, which wears the drivetrain faster and usually has an equivalent gear on the other ring. The summary counts distinct gears, treating any two gears within 3% of each other as one, which is why a 2 × 12 setup has 24 combinations but far fewer genuinely different gears.
1x or 2x?
Two chainrings give you more range and smaller steps; one chainring is simpler and lighter but has to choose between range and step size. Load a 2x road setup and a 1x gravel setup side by side and the chart makes the trade-off obvious. Whatever you ride, the other half of going fast is grip and comfort, so pair this with our tyre pressure calculator, and if your knees complain on long climbs, check your saddle height before blaming the gears.
Frequently asked questions
What gear ratio do I need for climbing?
As a rule of thumb, an easiest gear of around 1:1 (for example a 34-tooth chainring with a 34-tooth sprocket) lets most riders keep spinning on long climbs of 8–10%. Lighter or stronger riders get away with harder gears; heavier riders, loaded bikes and steeper gradients benefit from going below 1:1. If you find yourself grinding at under 70 rpm on your regular climbs, a lower easiest gear will help.
Will a bigger cassette make climbing easier?
Yes, by exactly the ratio of the largest sprockets. Going from a 30-tooth to a 34-tooth largest sprocket with the same chainring makes your easiest gear about 12% lower, so the same climb needs about 12% less force on the pedals at the same speed. The trade-off is usually bigger jumps between gears, and you may need a longer derailleur cage or a different derailleur to fit it.
What are gear inches and development?
Both describe how hard a gear is, including your wheel size. Development (or rollout) is how far the bike travels for one full pedal turn, in metres. Gear inches is an older measure: the gear ratio multiplied by the wheel diameter in inches. Both let you compare gears across bikes with different wheels, which a bare ratio like 50/17 cannot.
Is 1x or 2x gearing better?
A 2x drivetrain gives a wider range and smaller steps between gears, which suits road riding and group rides where cadence matters. A 1x drivetrain is simpler, lighter and less fussy in mud, at the cost of bigger jumps between gears or a narrower range. Compare both here: the gear chart shows the steps, and the summary shows how many genuinely different gears each setup has.
What is cross-chaining and should I avoid it?
Cross-chaining means running the big chainring with the largest sprockets, or the small chainring with the smallest ones. The chain runs at a steep angle, which wears the chain, chainrings and sprockets faster, adds friction and noise, and can cause rubbing. On a 2x setup there's almost always a similar gear on the other chainring, so shift rings instead. The chart greys out these combinations.