Bike Gear Ratio Calculator

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Walk-through

How to Use This Calculator

3 steps

1

Enter your chainring and cog

Type in the number of teeth on your front chainring and the rear cog you're comparing. Try a preset like Climbing (34/28) or Top Gear (50/14) to see how the numbers change. The gear ratio updates instantly as you type.

2

Pick your wheel size

Choose a common wheel size (700c road, 27.5", 29er, or 26" MTB) or type an exact tire diameter in inches. Gear inches and development both scale directly with wheel size, so a small wheel change shifts every downstream number.

3

Add a cadence to see speed

Enter your pedaling cadence in RPM to see your speed in mph and km/h for that gear. Switch to the Gear Inches tab to compare your chainring against a full cassette, or the Speed at Cadence tab to see how speed scales from an easy spin to a sprint.

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Reference

Formula & Methodology

4 formulas

Gear ratio

gear ratio = chainring teeth ÷ cog teeth

The gear ratio is simply the chainring tooth count divided by the rear cog tooth count. A 50-tooth chainring with a 14-tooth cog gives 50 ÷ 14 = 3.57 — the rear wheel spins 3.57 times for every one full pedal revolution.

Gear inches

gear inches = gear ratio × wheel diameter (in)

Gear inches multiplies the ratio by the wheel's outer diameter in inches. It's the classic penny-farthing-equivalent measurement: the diameter of a direct-drive wheel that would produce the same distance per pedal stroke, which lets you compare gearing fairly across different wheel and tire sizes.

Development

development = gear inches × π

Development (also called roll-out) is the actual distance the bike travels for one complete pedal revolution — the circumference of the equivalent gear-inches wheel. The calculator shows it in both inches and meters.

Speed at cadence

speed = development × cadence

Multiplying development (distance per pedal stroke) by cadence (pedal strokes per minute) gives distance per minute, which the calculator converts to mph and km/h.

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Glossary

Key Terms Explained

7 terms

Gear ratio The number of chainring teeth divided by the number of rear cog teeth. Larger ratios (big chainring, small cog) are harder to pedal but cover more ground per stroke; smaller ratios are easier but slower per stroke.

Gear inches Gear ratio multiplied by wheel diameter in inches, expressed as the equivalent direct-drive wheel size. Typical road gears run from roughly 30 gear inches (easiest climbing gear) to over 120 gear inches (hardest sprinting gear).

Development The distance traveled in one full pedal revolution, equal to gear inches × π. Also called roll-out or meters of development, most often quoted in meters for track and time-trial gearing.

Chainring The toothed sprocket attached to the crank arms that the pedals turn directly. Road bikes typically run 34–53 teeth; a bike may have one, two, or three chainrings.

Cog One of the toothed sprockets on the rear cassette that the chain engages. Modern cassettes typically span 10–36+ teeth across 9 to 13 cogs.

Cadence Pedaling speed measured in revolutions per minute (rpm). Most cyclists find 80–100 rpm efficient for sustained road riding; climbing cadence is often lower and track sprinting cadence much higher.

Wheel size The outer diameter of the wheel and tire together, in inches. Common bicycle wheel sizes are 700c (road, ~27"), 27.5" and 29" (mountain bike), and 26" (older mountain bikes and some hybrids).

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Scenarios

Real-World Examples

3 worked examples

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Road cyclist in top gear

50-tooth chainring, 14-tooth cog, 700c (27") wheel

Chainring 50 teeth Cog 14 teeth Wheel 27 in

Gear ratio = 50 ÷ 14 = 3.57:1, and gear inches = 3.57 × 27 = 96.4. That's a hard top-end gear — every pedal stroke covers about 302.9 inches (7.7 meters) of ground. At a cadence of 90 rpm this gear produces roughly 41.6 km/h (25.8 mph), which is why it's typically saved for descents and flat sprints.

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Climber shifting into an easy gear

34-tooth chainring, 28-tooth cog, 700c (27") wheel

Chainring 34 teeth Cog 28 teeth Wheel 27 in

Gear ratio drops to 34 ÷ 28 = 1.21:1, and gear inches falls to just 32.8 — roughly a third of the sprint example. Each pedal stroke covers only about 103 inches (2.6 meters), which is exactly what a lower gear is for: it trades distance per stroke for pedaling ease on a steep climb.

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Comparing speed at different cadences

Same 50/14 top gear, cadence varied from 70 to 110 rpm

Development 7.7 m Cadence range 70–110 rpm

At a fixed gear, speed scales linearly with cadence: 70 rpm gives about 32.3 km/h (20.1 mph), while 110 rpm gives about 50.8 km/h (31.6 mph). The Speed at Cadence tab lays out this full range so you can see exactly how much cadence — not just gearing — controls your speed.

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Deep Dive

Understanding Bike Gear Ratios

3 chapters · 4 min read

Bicycle gearing determines how hard each pedal stroke feels and how far it moves you. This calculator turns your chainring, cog, and wheel size into three standard gearing measurements — gear ratio, gear inches, and development — plus the speed those numbers produce at any cadence.

How the Bike Gear Ratio Calculator works

The calculator starts with the simplest measure, gear ratio: chainring teeth divided by cog teeth. A higher ratio means the rear wheel spins more times per pedal stroke — harder to push but faster per revolution. It then multiplies that ratio by your wheel's diameter in inches to get gear inches, a measurement cyclists have used for well over a century to compare gearing across different wheel sizes on equal footing. Multiplying gear inches by π gives development: the actual distance traveled per pedal revolution, shown in both inches and meters. Finally, multiplying development by your cadence (in revolutions per minute) gives speed, converted to both mph and km/h.

Inputs and what they mean

Chainring and cog are entered as tooth counts — count the teeth directly or check your component's spec sheet or box, since tooth counts are usually stamped on the part itself. Wheel size is the outer diameter of the wheel and tire together in inches; use the quick presets for common sizes (700c road, 27.5" or 29" mountain, 26" older mountain/hybrid) or enter an exact measured diameter for precision. Cadence is optional — leave it blank to see just the gearing numbers, or enter your typical pedaling rpm to see projected speed. The Gear Inches tab shows how your chainring pairs with every cog on a typical cassette, and the Speed at Cadence tab shows how speed scales across a full cadence range for your current gear.

Limits and edge cases

The calculator assumes a direct chainring-to-cog drivetrain (standard derailleur or single-speed gearing) and does not account for drivetrain losses, tire pressure, or rolling resistance — real-world speed will be slightly lower than the theoretical figure shown here. A cog value of zero or blank is rejected rather than producing a divide-by-zero error. Wheel diameter should reflect the actual rolling diameter of the tire mounted on the rim, not just the rim's bead-seat diameter, since tire width and profile shift the effective diameter by a small but measurable amount.

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Questions

Frequently Asked Questions

6 questions

What is the gear ratio formula?+

Gear ratio equals the number of teeth on the chainring divided by the number of teeth on the rear cog. A 50-tooth chainring paired with a 14-tooth cog gives a ratio of 50 ÷ 14 = 3.57:1 — the rear wheel turns 3.57 times for every one pedal revolution.

What are gear inches?+

Gear inches is the gear ratio multiplied by the wheel diameter in inches. It expresses gearing as the effective diameter of an old-style direct-drive wheel that would give the same distance per pedal stroke, which makes it easy to compare gears across different wheel sizes.

What is development in cycling?+

Development (also called roll-out or meters of development) is the distance the bike travels for one full pedal revolution. It equals gear inches multiplied by pi — the circumference of the equivalent wheel — and is commonly expressed in meters.

How do I calculate speed from cadence and gearing?+

Multiply the development (distance per pedal revolution) by your cadence in revolutions per minute to get distance per minute, then convert to your preferred speed unit. For example, a development of 7.7 meters at a cadence of 90 rpm gives roughly 41.6 km/h (25.8 mph).

Is a bigger gear ratio better?+

A bigger gear ratio (large chainring, small cog) covers more distance per pedal stroke and is harder to turn — good for flat ground and high speed. A smaller ratio (small chainring, large cog) is easier to pedal and better suited to climbing.

What units does the calculator use?+

Chainring and cog are entered as tooth counts, wheel diameter in inches, gear inches in inches, development in both inches and meters, and speed in both mph and km/h.

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Gear Inches Across Your Cassette

Speed at Different Cadences

How to Use This Calculator

Enter your chainring and cog

Pick your wheel size

Add a cadence to see speed

Formula & Methodology

Key Terms Explained

Real-World Examples

Road cyclist in top gear

Climber shifting into an easy gear

Comparing speed at different cadences

Understanding Bike Gear Ratios

How the Bike Gear Ratio Calculator works

Inputs and what they mean

Limits and edge cases

Frequently Asked Questions

Get a branded PDF of your results

Bike Gear Ratio Calculator

Gear Inches Across Your Cassette

Speed at Different Cadences

How to Use This Calculator

Enter your chainring and cog

Pick your wheel size

Add a cadence to see speed

Formula & Methodology

Key Terms Explained

Real-World Examples

Understanding Bike Gear Ratios

How the Bike Gear Ratio Calculator works

Inputs and what they mean

Limits and edge cases

Frequently Asked Questions

Get a branded PDF of your results

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