Fixed Gear Ratio Calculator

Enter your bike’s specifications to calculate your gear ratio, gear inches, skid patches, and potential speed. This tool is essential for any rider using a fixed gear ratio calculator.

Gear Inch Comparison Table

Cog Size	Gear Ratio	Gear Inches

Compares gear inches for different cog sizes using your current chainring and wheel setup.

What is a Fixed Gear Ratio?

A fixed gear ratio is the heart of a single-speed or ‘fixie’ bicycle. It represents the mechanical relationship between the front gear (chainring) and the rear gear (cog). Calculated by dividing the number of teeth on the chainring by the number of teeth on the cog, this single number dictates how many times the rear wheel rotates for one full turn of the pedals. Unlike multi-speed bikes, this ratio is constant, defining the bike’s performance characteristics. This simplicity is cherished by purists and urban cyclists, but it requires a deep understanding to get the setup right. A proper fixed gear ratio calculator is an indispensable tool for this.

Anyone from a track racer optimizing for explosive speed to a city commuter looking for a reliable, low-maintenance ride should use a fixed gear ratio calculator. A common misconception is that a single ratio is good for all situations. In reality, the ideal ratio is a highly personal choice depending on the rider’s strength, typical terrain, and desired riding feel. Another myth is that it’s all about the ratio; in fact, related metrics like gear inches and skid patches are just as crucial for a well-rounded setup.

Fixed Gear Ratio Formula and Mathematical Explanation

The mathematics behind the fixed gear ratio calculator are straightforward but powerful. The core formulas allow riders to quantify their setup and make informed decisions.

1. Gear Ratio: The primary calculation. It’s the foundation for all other metrics.
Gear Ratio = Teeth on Chainring / Teeth on Cog

2. Gear Inches: This is a more comprehensive metric that includes the wheel size, providing a standardized way to compare gearing across different bikes. It represents the effective diameter of the drive wheel. A higher gear inch value means a ‘harder’ gear, covering more distance per pedal revolution.
Gear Inches = Gear Ratio * Total Wheel Diameter in Inches

3. Skid Patches: A unique metric for fixed-gear riders. It indicates how many distinct points on the rear tire will contact the ground when skidding to a stop. More patches mean more even tire wear. The calculation involves finding the greatest common divisor (GCD) of the chainring and cog teeth.
Skid Patches = Cog Teeth / GCD(Chainring Teeth, Cog Teeth)

Variable	Meaning	Unit	Typical Range
Chainring Teeth	Number of teeth on the front gear.	Teeth	42 – 55
Cog Teeth	Number of teeth on the rear gear.	Teeth	13 – 22
Wheel Diameter	Combined diameter of rim and tire.	Inches	26″ – 29″
Gear Ratio	Revolutions of the wheel per pedal crank.	Ratio	2.0 – 3.5
Gear Inches	Standardized measure of gearing effort.	Inches	60 – 100

Practical Examples (Real-World Use Cases)

Example 1: The Urban Commuter

An urban rider in a moderately hilly city wants a balance between speed on flats and climb-ability. They use a fixed gear ratio calculator to find a good starting point.

• Inputs: Chainring = 46T, Cog = 18T, Wheel/Tire = 700x28c (approx. 27.2″ diameter)
• Calculator Output:
  • Gear Ratio: 2.56
  • Gear Inches: 69.5
  • Skid Patches: 9 (since GCD(46, 18) = 2, 18/2 = 9)
• Interpretation: The gear inches around 70 are considered a versatile sweet spot—not too hard for moderate inclines, but still efficient for cruising. Having 9 skid patches provides decent tire longevity. This is a great example of using a fixed gear ratio calculator for practical city riding.

Example 2: The Track Sprinter

A track cyclist needs a high gear for maximum speed on the velodrome. Acceleration is less of a concern than top-end velocity. They consult a cadence calculator along with the fixed gear ratio calculator.

• Inputs: Chainring = 52T, Cog = 15T, Wheel/Tire = 700x23c (approx. 27.0″ diameter)
• Calculator Output:
  • Gear Ratio: 3.47
  • Gear Inches: 93.6
  • Skid Patches: 15 (since 52 and 15 are coprime, GCD=1)
• Interpretation: The high gear inches (over 90) are built for speed. At a high cadence of 120 RPM, this setup would yield over 33 mph. The 15 skid patches are a bonus, ensuring the expensive track tires wear evenly during training.

How to Use This Fixed Gear Ratio Calculator

This fixed gear ratio calculator is designed to be intuitive yet powerful. Follow these steps to analyze your gearing:

1. Enter Chainring Teeth: Input the number of teeth on your front chainring. This is a primary driver of your overall speed potential.
2. Enter Cog Teeth: Input the number of teeth on your rear cog. A smaller cog results in a higher (harder) gear ratio.
3. Select Wheel and Tire Size: Choose your rim size (e.g., 700c) and enter your tire width in millimeters. The calculator uses these to find the precise overall diameter for accurate gear inch calculations.
4. Set Your Cadence: Enter your typical or target pedaling speed in RPM. This is used to estimate your road speed.
5. Analyze the Results: The calculator instantly updates. The “Gear Ratio” is your primary metric. “Gear Inches” gives a standardized value for effort. “Skid Patches” tells you about tire wear. “Speed at Cadence” gives you a real-world speed estimate.
6. Use the Dynamic Tools: Check the “Speed vs. Cadence” chart to see your potential across different efforts. Consult the “Gear Inch Comparison Table” to see how changing your cog would affect your ride, a key function of any advanced fixed gear ratio calculator.

Key Factors That Affect Fixed Gear Ratio Results

Choosing the right gearing is more than just numbers; it’s about how those numbers interact with you and your environment. A fixed gear ratio calculator helps quantify these factors.

• Rider Fitness and Strength: A stronger rider can push higher gear inches, achieving greater speeds. A beginner should start with a lower, more forgiving ratio (e.g., 2.5-2.8).
• Terrain: Flat cities are ideal for higher ratios (3.0+). Hilly environments demand lower ratios (2.4-2.7) to make climbing manageable without exhausting the rider.
• Wheel and Tire Size: As seen in the gear inch formula, a larger wheel/tire combination increases the final gear inches, making the gear feel harder. A switch from a 23c to a 32c tire can be noticeable. Consider a bicycle tire size calculator for specifics.
• Intended Use: Track racing requires high ratios for speed. Trick riding and bike polo benefit from lower ratios for acceleration and control. Urban commuting sits in the middle. The fixed gear ratio calculator is a tool for every discipline.
• Cadence: A rider who prefers to spin at a high cadence (90+ RPM) might choose a lower gear ratio to stay in their comfort zone, while a “masher” who pedals slowly with more force will opt for a higher ratio.
• Skid Patches & Tire Longevity: For riders who skid to stop, maximizing skid patches is crucial for saving money on tires. Using prime numbers for your cog (like 13, 17, 19) often results in the highest number of skid patches.

Frequently Asked Questions (FAQ)

What is the best all-around fixed gear ratio?

A ratio around 2.7-2.8 (like 46/17 or 48/17) is often cited as a versatile starting point, yielding gear inches in the mid-70s. However, the best ratio is personal, and you should use a fixed gear ratio calculator to find your own sweet spot.

How does a skid patch calculator work?

It calculates the number of unique wear points on your tire when braking. It does this by simplifying the fraction of your chainring and cog teeth and using the denominator. A higher number is better for tire life. Our fixed gear ratio calculator includes this feature automatically.

Does gear ratio affect my ability to go up hills?

Absolutely. A lower gear ratio (e.g., 44/18) results in lower gear inches, making it easier to pedal up steep inclines. A high ratio can make climbing feel impossible.

What’s the difference between gear ratio and gear inches?

Gear ratio is just the division of the two sprockets (e.g., 48/16 = 3.0). Gear inches provides more context by including the wheel’s diameter in the calculation, making it a standardized measure that is comparable across different bike setups.

Why do prime numbers matter for cogs?

Using a cog with a prime number of teeth (like 13, 17, 19) makes it less likely to share a common divisor with your chainring. This results in a higher number of skid patches, which is a key consideration for many who use a fixed gear ratio calculator.

Can I change my gear ratio?

Yes, easily. You can either change your front chainring or your rear cog. Changing the cog is typically easier and cheaper. A one-tooth change in the cog has a more significant impact than a one-tooth change in the chainring.

Is a higher gear ratio always faster?

Not necessarily. A higher ratio provides a higher top speed *if* the rider has the strength to get it up to an effective cadence. If the gear is too high, the rider may struggle to pedal it fast enough, resulting in a lower overall speed than a more manageable, lower gear ratio.

How does a track bike gearing differ from road gearing?

Track bikes typically use much higher gear ratios because there are no hills and the goal is pure speed. A typical track setup might be 48/15 or higher, something you’d rarely use for daily street riding. This is where a fixed gear ratio calculator is vital for context.

Related Tools and Internal Resources

For more in-depth analysis and related topics, explore our other calculators and guides:

• Gear Inches Calculator: A focused tool for calculating and comparing gear inches for any bicycle.
• Skid Patch Calculator: Dive deeper into calculating skid patches to maximize your tire’s lifespan.
• Fixed Gear Maintenance: Learn how to keep your single-speed bike in top condition.
• How to Build a Fixie: A step-by-step guide to building your own fixed-gear bicycle from the frame up.
• Finding the Best Fixie Ratio: A detailed article on the art and science of selecting the perfect ratio for your needs.
• Single Speed Gear Ratio: Another great resource to help you with your calculations.