Gear Inches Calculator

Calculate gear inches for comparing gearing across different wheel sizes. The universal metric for comparing bicycle gearing.

Results

Visualization

How It Works

Gear inches = (chainring/cog) x tire diameter in inches. It originated from the penny-farthing era, representing the equivalent diameter of a direct-drive wheel. Gear inches let you compare gearing between bikes with different wheel sizes (700c road vs 26" MTB vs 20" BMX). Below 20 gear inches = extremely low mountain gearing. 60-80 gear inches = typical road cruising range. Above 110 = racing top gear. Sheldon Brown popularized gear inches as the best single number for comparing bicycle gearing.