Don't like ads? Go Ad-Free Today 

Bicycle Gear Ratio & Speed Calculator

DeveloperMath

ADVERTISEMENT · REMOVE?

INPUT

Auto Process

Drivetrain

Chainrings *

Comma-separated chainring tooth counts (front). Order: largest first.

Cassette Sprockets *

Comma-separated rear sprocket tooth counts. Order: smallest first.

Wheel

Wheel Size

Custom Circumference

Rolling circumference in millimetres (one full wheel revolution).

Cadence & Units

Cadence (RPM): 90 Pedal revolutions per minute. Recreational ≈ 70–80, road ≈ 85–95, racers ≈ 100+.

Speed Unit

Display

Grid Shows

OUTPUT

Client Side

Summary

Property	Value
Wheel Circumference	-
Total Gear Combinations	-
Lowest Gear (easiest climbing)	-
Highest Gear (top speed)	-
Gear Range	-
Speed in Lowest Gear	-
Speed in Highest Gear	-

Gear Grid

Enter chainrings and sprockets to see every gear combination.

Adjust cadence with the slider to see live speed updates. Cells highlighted in amber indicate gear overlap between chainrings.

ADVERTISEMENT · REMOVE?

Guide

Bicycle Gear Ratio & Speed Calculator

See exactly how fast you will roll in every gear on your bike. Punch in your chainring and cassette teeth, pick a wheel size, and the calculator builds a colour-coded grid of speed, gear inches, development and ratio for every chainring × sprocket combination — useful when shopping for a new groupset, planning a build, or hunting down duplicate gears you never use.

How to Use

Enter your chainring tooth counts as a comma list (e.g. 50, 34 for a 50/34 compact crank).
Enter your cassette sprocket tooth counts smallest first (e.g. 11, 13, 15, 17, 19, 21, 24, 28, 32).
Pick a wheel size preset that matches your tyre, or choose Custom and type the rolling circumference in millimetres.
Drag the cadence slider to your usual RPM (recreational ≈ 75, road ≈ 90, racers 100+) and pick km/h or mph.
Use the Grid Shows dropdown to swap between speed, gear inches, development, or raw ratio. The summary table updates with low/high gear, gear range and top speed live.
Cells highlighted in amber are overlapping gears between your chainrings — gears that duplicate within 5% and can be skipped when shifting.

Features

Every combination at a glance – chainring × sprocket grid with all gears side by side, not one at a time.
Multiple metrics – switch the grid between speed, gear inches, metres of development, or gear ratio.
Wheel size presets – 700×23/25/28/32/38c, 650b gravel, 26″, 27.5″, 29″ MTB, 20″ BMX, 16″ folding, plus a custom circumference field.
Speed at your cadence – slider from 40 to 120 RPM with km/h or mph output.
Overlap detection – cells across chainrings within 5% ratio are flagged amber so you can spot duplicate gears.
Lowest and highest gear highlighted – easiest climbing gear in green, top-speed gear in orange.
Live summary – wheel circumference, total combinations, gear range percentage, and top/bottom speeds at the selected cadence.
Client-side only – no uploads, no accounts, nothing leaves your browser.

 FAQ

What is a gear ratio on a bicycle?

Gear ratio is the front chainring tooth count divided by the rear sprocket tooth count. A 50t chainring with a 25t sprocket gives a ratio of 2.0, meaning one pedal revolution turns the rear wheel two full times. Higher ratios travel further per pedal stroke but require more force; lower ratios spin faster for the same effort, ideal for climbing.
What are gear inches and why are they used?

Gear inches is the effective diameter of the rear wheel if the bike had no gears: wheel diameter (inches) × gear ratio. It dates back to high-wheeler bikes where you simply quoted the wheel size. Today it is a wheel-size-independent way to compare gearing — 100 gear inches feels the same on any bike, whether 700c road or 29er MTB.
What is development (or roll-out) and how does it differ from gear inches?

Development is the distance the bike travels in one pedal revolution, measured in metres: wheel circumference × gear ratio. It is the European equivalent of gear inches and is more intuitive for actual cycling — a development of 8 metres means each pedal stroke moves you 8 metres along the road.
Why do some cassettes have overlapping gears between chainrings?

On a 2x drivetrain (two chainrings), some chainring/sprocket combinations end up with nearly identical ratios — for example 50/19 and 34/13 both give ratios near 2.6. These are 'overlap' gears: shifting between them changes nothing in feel or speed. Modern 1x drivetrains were designed to eliminate this duplication, simplifying gear choice at the cost of bigger jumps between gears.