Gear ratio
Gear ratio is simply chainring teeth ÷ cog teeth. A 50T chainring with a 14T cog is 3.57:1 — your wheel turns 3.57 times for every pedal stroke.
Gear inches
Gear inches multiply the ratio by the wheel diameter in inches, giving a single number you can compare across wheel sizes. Higher = harder/faster.
Development
Development is how far the bike travels per pedal revolution, in metres — the most intuitive figure of all. Try all three on the gearing converter.