How it works
gear inches = (chainring teeth ÷ cog teeth) × wheel diameter (in)
This page keeps the calculation centered on one relationship: gear inches = (chainring teeth ÷ cog teeth) × wheel diameter (in). Inputs are normalized before the final display, which keeps mile, kilometer, pace, speed, or zone outputs from drifting because of rounding. Use the number as a consistent model output, then layer in terrain, weather, recovery, and race execution. Keep the fixed reference values in view: 30, 120, 700, 25, 26.4.
Sources
- Gear inches and gain ratio Sheldon Brown — Bicycle Gearing: gear inches = (chainring ÷ cog) × wheel diameter; gain ratio uses wheel radius ÷ crank length. sheldonbrown.com/gears
- Development (roll-out per pedal stroke) Metres of development = gear inches × π × 0.0254 — the distance the bike travels for one full crank revolution.
- 700c wheel diameter A 700×25c tyre on an ISO 622 rim has an outer diameter of roughly 670 mm ≈ 26.4 inches, the standard road-bike reference.
FAQ
When should I use the gear inches calculator?
Use it when you want a fast planning number before a run, race, workout, or gear decision. It gives you a consistent estimate without asking you to create an account. Keep the fixed reference values in view: 30, 100.
What inputs matter most?
The best result comes from honest, current inputs. Recent race times, realistic body measurements, accurate workout data, and the correct unit setting matter more than perfect formatting. Keep the fixed reference values in view: 700, 25, 26.4, 28, 26.5, 26, 26.0.
How should I read the result?
Treat the output as a planning reference, not a promise. Use it to compare options, set a target range, or sanity-check your watch data before making the final call. Keep the fixed reference values in view: 70, 5.6 m.
Does this work in miles and kilometers?
Yes. PacerRunning is written for US runners first, so miles are easy to use, but metric conversions are kept alongside them where the tool needs both views.
Why might my real-world result differ?
Terrain, wind, heat, sleep, fueling, training fatigue, and measurement error can all move the real outcome away from the estimate. The Gear Inches gear inches calculator cannot see those details. Keep the fixed reference values in view: 50, 17, 34, 11.
Can beginners use it?
Yes. You do not need advanced training knowledge. Enter the numbers you know, read the result as a guide, and keep your effort comfortable when you are unsure.
Gear Inches Calculator results are estimates from the entered data and the cited method. They are useful for planning and comparison, but they are not a diagnosis, prescription, guaranteed race result, or substitute for a coach or clinician. Keep the fixed reference values in view: 172.5 m.