Ratio Fixie Calculator
Calculate your Gear Ratio, Gear Inches, Meters Development, and Skid Patches for fixed gear bicycles.
3.00
79.0″
6.32 m
1
34.1 km/h
Gear Development Comparison
Comparing current ratio development vs common cog variations (+1/-1 tooth)
| Cog Size | Ratio | Skid Patches | Ambi Patches* |
|---|
*Ambidextrous patches: total patches available if you can skid with either foot forward.
What is a Ratio Fixie Calculator?
A ratio fixie calculator is an essential tool for fixed-gear cyclists (track riders, urban commuters, and freestyle riders) to determine the mechanical relationship between their front chainring and rear cog. Unlike geared bicycles, a fixed gear bike relies on a single gear ratio that determines everything from top speed to how difficult it is to stop the bike using back-pressure.
Using a ratio fixie calculator allows riders to find the “sweet spot” where they have enough torque to climb hills but sufficient top-end speed for flats. It also helps calculate skid patches, which are specific spots on the rear tire that wear down when skidding. If your ratio fixie calculator shows you only have one skid patch, you will wear through your tire very quickly.
Ratio Fixie Calculator Formula and Mathematical Explanation
The math behind a ratio fixie calculator involves three primary metrics: Simple Ratio, Gear Inches, and Development. Here is how we derive these values:
1. Gear Ratio: This is the simplest calculation.
Ratio = Chainring Teeth / Cog Teeth
2. Gear Inches: This represents the diameter of an equivalent “Penny Farthing” wheel.
Gear Inches = (Chainring / Cog) * Wheel Diameter (inches)
3. Meters Development: This is the distance the bike travels with one full rotation of the pedals.
Development = (Chainring / Cog) * Tire Circumference (meters)
Variable Definitions Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Chainring | Front gear teeth count | Count | 42 – 52 |
| Rear Cog | Rear gear teeth count | Count | 13 – 19 |
| Wheel Dia. | Effective height of the wheel | Inches | 26 – 28 |
| Cadence | Pedal revolutions per minute | RPM | 70 – 110 |
Practical Examples (Real-World Use Cases)
Example 1: The Urban Commuter
A rider uses a 48t chainring and a 16t cog. Inputting these into the ratio fixie calculator yields a 3.00 ratio. While this is great for speed, the ratio fixie calculator reveals only 1 skid patch. If the rider skids, they will blow out their tire in days. By switching to a 17t cog, they increase patches to 17, vastly extending tire life.
Example 2: The Track Sprinter
A racer at the velodrome uses a 50t chainring and a 14t cog. The ratio fixie calculator shows a high gear inch value of ~96″. This allows the rider to reach high speeds at a lower RPM, which is critical for sprint finishes where aerodynamics and power transfer are paramount.
How to Use This Ratio Fixie Calculator
- Enter Chainring: Input the number of teeth on your front crank gear.
- Enter Cog: Input the number of teeth on your rear hub gear.
- Select Tire: Choose your tire size (most fixies use 700x25c).
- Check Skid Patches: Look at the skid patch result. Aim for a number higher than 5 to save money on tires.
- Analyze Speed: Adjust the cadence to see your potential top speed with that specific gear setup.
Key Factors That Affect Ratio Fixie Calculator Results
- Chainring Teeth: Larger rings increase top speed but make starting and climbing harder.
- Cog Teeth: Smaller cogs increase the ratio significantly. A 1-tooth change on the back is much more impactful than 1 tooth on the front.
- Tire Width: A 28c tire has a larger circumference than a 23c tire, effectively increasing your gear inches even if the ratio stays the same.
- Crank Length: While not in the base ratio, longer cranks provide more leverage for starting, though they increase the risk of pedal strike in corners.
- Mechanical Efficiency: A worn chain or dirty drivetrain can make a “light” ratio feel heavy.
- Rider Weight/Power: A heavy ratio (high gear inches) requires more leg strength to accelerate from a standstill.
Related Tools and Internal Resources
- Bike Maintenance Guide: Learn how to install your new cog after using the ratio fixie calculator.
- Skid Patch Masterlist: A deep dive into the math of tire wear for fixed gear bikes.
- Cadence to Speed Chart: Detailed tables for various ratios and RPMs.
- Velodrome Gear Selection: Professional advice on choosing the right track ratio.
- Chain Line Alignment: Ensuring your fixie runs silent and efficient.
- Fixed Gear Safety: Why brakes are still a good idea even with a perfect ratio.
Frequently Asked Questions (FAQ)
Is a higher ratio better?
Not necessarily. A higher ratio allows for higher top speeds but makes acceleration and hills very difficult. For urban riding, a moderate ratio is usually better.
What are skid patches?
Skid patches are the points on the tire that touch the ground when your pedals are locked. A ratio fixie calculator helps you maximize these to avoid burning a hole in your tire.
How do I increase my skid patches?
Try to use a rear cog with a prime number of teeth (like 17 or 19) or ensure the front and back tooth counts don’t share large common factors.
Does tire pressure affect the ratio?
Minutely. Lower pressure decreases the effective rolling radius, slightly shortening the gear inches, though this is rarely calculated by a standard ratio fixie calculator.
What is a good gear inch for beginners?
Most beginners find 65 to 75 gear inches to be the “sweet spot” for street riding.
Why do I need a ratio fixie calculator for track racing?
Track racers need to hit specific speeds at specific cadences. The ratio fixie calculator ensures they aren’t “spinning out” too early.
Can I use this for single speed bikes?
Yes, the ratio and gear inches will be the same, but you can ignore the skid patch calculation since you aren’t locking the wheel.
What is meters development?
It is simply how many meters your bike moves forward for every one full rotation of the pedals. It is the most accurate way to compare different wheel sizes.