Fixed Gear Ratio & Speed Calculator
Calculate your gear ratio, gear inches, rollout, estimated speed, gain ratio, and skid patches for a fixed gear bike.
What this fixed gear calculator does
A fixed gear bike has one gear, so your setup choice matters more than on a geared bike. This calculator helps you compare chainring and rear cog combinations quickly so you can choose a ratio that matches your roads, legs, and riding style.
Instead of guessing, you can see how each gearing option changes acceleration, top-end speed, cadence comfort, and skid patch count. Whether you ride city streets, rolling hills, or a velodrome, these numbers help you tune your bike with confidence.
How the math works
1) Gear ratio
The core number is:
Gear Ratio = Chainring Teeth / Rear Cog Teeth
A higher ratio means harder pedaling but more distance per pedal revolution.
2) Gear inches
Gear inches are a classic way to compare gearing:
Gear Inches = Gear Ratio × Wheel Diameter (inches)
This helps compare your setup with other bikes and historical track or road standards.
3) Development (rollout) and speed
Development is distance traveled per crank revolution:
Development (m/rev) = Gear Ratio × Wheel Circumference (m)
Then estimated speed is:
Speed = Cadence × Development
Higher cadence or higher development both increase speed.
4) Gain ratio and skid patches
Gain ratio includes crank length, giving a feel for leverage changes. Skid patches estimate rear tire wear distribution on a fixed gear:
- One-leg skid patches:
rear cog / gcd(chainring, rear cog) - Two-leg skid patches: usually doubles when the reduced chainring is odd
More skid patches generally means more even tire wear.
Choosing a ratio for your riding
City commuting
- Common range: 65–75 gear inches
- Good for starts, stoplights, and mixed terrain
- Examples: 44/17, 46/17, 48/18
Fast road riding
- Common range: 75–85 gear inches
- Better cruising speed on flatter routes
- Examples: 48/17, 49/17, 50/18
Track or very strong riders
- Often 85+ gear inches depending on event
- Higher speed potential, slower acceleration
- Examples: 49/15, 50/15, 52/16
Example setups (700c-style wheel)
- 42/17 — easy spin, great for hills and dense traffic.
- 46/16 — versatile all-round city ratio.
- 48/17 — balanced mix of acceleration and cruising.
- 49/15 — aggressive gearing for stronger riders on flatter routes.
Practical fixed gear tips
- Start slightly easier than you think, then gear up once your cadence control improves.
- For all-weather city use, prioritize chainline and tire clearance over chasing a huge gear.
- If you skid often, consider ratios with more skid patches to reduce uneven rear tire wear.
- Re-check chain tension after chainring or cog changes.
Bottom line
The best fixed gear ratio is the one you can spin smoothly, climb comfortably, and ride safely every day. Use the calculator above to test combinations before buying parts, then fine-tune based on real rides.