Fixed Gear Ratio Calculator

Calculate your bicycle gear ratio, gear inches, development, and skid patches instantly.

Common Fixed Gear Ratios Table

Chainring	Cog	Ratio	Gear Inches (700×25)	Skid Patches
44	17	2.59	69.9	17
46	16	2.88	77.7	8
48	17	2.82	76.3	17
48	15	3.20	86.4	5
49	17	2.88	77.8	17

What is a Fixed Gear Ratio Calculator?

A fixed gear ratio calculator is an essential tool for track cyclists, urban commuters, and fixed-gear enthusiasts. Unlike multi-speed bikes, a fixed-gear (or “fixie”) drivetrain lacks a freewheel mechanism, meaning the pedals turn whenever the rear wheel moves. Choosing the right gear ratio is critical because it dictates how hard you have to pedal to start, your top speed, and your ability to brake using back-pressure.

Who should use it? Anyone building a track bike, converting an old road frame, or looking to optimize their skid patch calculator results. A common misconception is that a “bigger” ratio is always better. In reality, the perfect ratio depends on your terrain, fitness, and whether you need to skid often.

Fixed Gear Ratio Calculator Formula and Mathematical Explanation

The math behind a fixed gear ratio calculator involves several variables related to gear teeth and wheel dimensions. The primary calculation is the mechanical advantage of the drivetrain.

The Core Formulas:

• Gear Ratio: Chainring Teeth / Cog Teeth
• Gear Inches: (Chainring / Cog) × Wheel Diameter (inches)
• Development (Meters of Development): (Chainring / Cog) × Wheel Circumference (meters)
• Skid Patches: The denominator of the simplified ratio (Chainring / Cog).

Variable	Meaning	Unit	Typical Range
Chainring	Front sprocket size	Teeth	42 – 52
Cog	Rear sprocket size	Teeth	13 – 19
Cadence	Pedaling speed	RPM	70 – 110
Wheel Diameter	Full height of tire	Inches/mm	622mm – 700mm

Practical Examples (Real-World Use Cases)

Example 1: The Urban Commuter

A rider uses a 46-tooth chainring and a 16-tooth cog on 700x25c tires. Using the fixed gear ratio calculator, we find a ratio of 2.88. This equates to roughly 77.7 gear inches. This is a balanced setup for flat city streets, offering decent acceleration and a manageable top speed.

Example 2: The Track Racer

A racer on a velodrome might use a 49×14 setup. The fixed gear ratio calculator shows a high ratio of 3.50 (94.5 gear inches). While this would be very difficult to start from a standstill at a red light, it allows for extreme speeds at high cadences during a race.

How to Use This Fixed Gear Ratio Calculator

Following these steps ensures you get the most accurate results for your bike setup:

1. Enter Chainring: Input the number of teeth on your front crank.
2. Enter Cog: Input the number of teeth on your rear wheel sprocket.
3. Select Tire Size: Choose your tire width to calculate bicycle gear ratio metrics like speed and gear inches accurately.
4. Set Cadence: Input your average pedaling RPM (90 is a standard benchmark).
5. Review Results: Look at the “Skid Patches” if you plan to skid-brake to ensure you aren’t wearing through your tires too fast.

Key Factors That Affect Fixed Gear Ratio Calculator Results

• Terrain: Hilly areas require a lower gear ratio (e.g., 2.4 – 2.6) while flat areas allow for higher ratios (2.8 – 3.1).
• Tire Width: A wider tire increases the effective wheel diameter, slightly increasing your gear inches even with the same sprockets.
• Crank Arm Length: While not in the ratio formula, longer cranks provide more leverage, making a “heavy” gear feel lighter.
• Skid Patches: Prime numbers for cogs (like 17 or 19) usually provide more skid patch calculator options, extending tire life.
• Drivetrain Efficiency: A clean, well-tensioned chainline alignment improves the feel of any ratio.
• Fitness Level: Higher strength allows for higher track racing gears, but spinning a lighter gear is often better for knee health.

Frequently Asked Questions (FAQ)

What is a good gear ratio for a beginner?

A ratio between 2.6 and 2.8 (e.g., 46/17 or 44/16) is generally recommended for beginners as it balances speed and ease of pedaling.

Why are skid patches important?

Skid patches are the specific points on your tire that hit the ground when you lock your legs to skid. More patches mean more even tire wear.

How do I calculate gear inches?

Multiply the gear ratio by the diameter of the wheel in inches. A fixed gear ratio calculator automates this for you.

What are “meters of development”?

It is the distance the bike travels with one full revolution of the pedals. It’s the metric version of gear inches.

Is a 3.0 ratio too heavy for city riding?

For most people, yes. A 3.0 ratio (like 48/16) can be tough on the knees during frequent stop-and-go traffic.

Do tire sizes really change the ratio?

They don’t change the mechanical ratio, but they change the “output” ratio (Gear Inches), which affects how the bike feels.

How does cadence affect my speed?

Higher cadence calculator values mean higher speeds for the same ratio. Efficient cyclists usually aim for 80-100 RPM.

Can I use this for a single-speed bike with a freewheel?

Yes, the ratio and gear inch calculations are the same, though “skid patches” won’t apply since you can’t skid with a freewheel.

Related Tools and Internal Resources

• Cadence Calculator – Determine your optimal pedaling speed for efficiency.
• Tire Size Guide – Find the exact circumference of your specific tires.
• Skid Patch Guide – Deep dive into maximizing your fixed gear tire life.
• Track Racing Gears – Professional setups for velodrome competition.
• Chainline Alignment – How to ensure your drivetrain is silent and efficient.
• Bicycle Speed Calculator – Calculate speed across various wheel and gear combinations.