fixie calculator

What a fixie calculator helps you decide

A fixed-gear bike has no coasting, no gear shifts, and no freewheel. That simplicity is part of the appeal, but it also means your drivetrain choice matters more than on a geared bike. This fixie calculator gives you practical numbers so you can choose a setup that matches your roads, fitness, and riding style.

Instead of guessing whether 46x16 or 49x17 feels better, you can compare objective metrics and quickly understand how each combination affects acceleration, top speed, leg fatigue, and tire wear from skids.

Key metrics explained

1) Gear ratio

Gear ratio is chainring teeth divided by cog teeth. A higher ratio means a harder gear: more distance per pedal revolution, more force needed to accelerate, and lower cadence for the same speed.

2) Gear inches

Gear inches normalize gearing by wheel diameter. It is useful for comparing setups across different wheel sizes. Urban fixed riders often choose moderate gear inches that allow quick starts at lights while still supporting cruising speed.

3) Rollout (development)

Rollout tells you how many meters the bike travels per crank revolution. This is one of the most intuitive values: if rollout is 6.0 m, each complete pedal turn moves you about six meters on flat ground.

4) Speed at cadence

Once you know rollout, speed is easy to estimate from cadence. This helps you answer practical questions such as:

• How fast will I cruise at 85–95 RPM?
• Will I spin out too early on descents?
• Will this ratio be comfortable in city traffic?

5) Gain ratio

Gain ratio includes crank length, giving a cleaner picture of pedaling leverage. Riders with shorter cranks may perceive a setup differently than riders on longer cranks, even with the same chainring and cog.

6) Skid patches

Skid patches estimate how many distinct tire contact points you create when skidding. More skid patches usually spread wear better and can increase tire life. This calculator shows one-foot skid patches and an adjusted estimate if you can skid with either foot forward.

How to choose gearing for your riding

City commuting

If your route has many stops, you usually benefit from a slightly easier gear. It improves low-speed control and reduces knee strain when accelerating repeatedly.

Mixed terrain

For rolling routes, choose a middle gear that keeps cadence in a comfortable band on flats while staying manageable on short climbs. Many riders target a setup that feels smooth around 85–100 RPM.

Fast group rides or velodrome-style efforts

Strong riders may choose a harder ratio for higher cruising speed. The tradeoff is tougher starts and heavier load at low cadence.

Example interpretation

Suppose you run 48x17 with a typical 700c road wheel. You may see a moderate gear ratio and a practical rollout for urban riding. If you change only the cog to 16, every pedal stroke moves the bike farther, but starts become punchier and skids demand more force.

• Go up one tooth in front → slightly harder gear.
• Go down one tooth in rear → noticeably harder gear.
• Bigger wheel/tire diameter → effectively harder gear.

Safety and fit reminders

Numbers help, but comfort and control are personal. Test changes gradually and keep your knees happy:

• Use a chainline that is straight and secure.
• Maintain correct chain tension and lockring installation.
• Practice high-cadence control before running a very hard ratio.
• Use reliable tires and inspect tread if you skid frequently.

Bottom line

The best fixed-gear ratio is the one that suits your daily terrain and riding goals. Use this fixie calculator as a decision aid, then validate on real rides. Small drivetrain changes can dramatically change feel, so iterate intentionally and track what works.