Fixed Gear Gear Ratio Calculator

The ultimate tool to analyze and select the perfect gearing for your fixie.

Cadence (RPM)	Speed (km/h)	Speed (mph)

Speed at different cadences for the selected gear ratio. This table helps visualize how fast you’ll be traveling while pedaling at a comfortable pace.

What is a Fixed Gear Gear Ratio?

A fixed gear gear ratio is the fundamental metric that defines how a single-speed or fixed-gear bicycle feels to ride. It represents the relationship between the number of teeth on the front chainring (connected to the pedals) and the number of teeth on the rear cog (connected to the rear wheel). This ratio dictates how many times the rear wheel rotates for every single revolution of the pedals. For instance, a gear ratio of 3.0 means the rear wheel turns exactly three times for each full pedal stroke. Understanding this is the first step in using a fixed gear gear ratio calculator effectively.

This calculator is for any cyclist on a fixed-gear or single-speed bike, from commuters and city riders to track racers and trick riders. The ideal ratio depends heavily on terrain, riding style, and physical strength. A common misconception is that a higher ratio is always better because it means a higher top speed. While true, a very high ratio can be difficult to accelerate from a stop and challenging to climb hills with. Conversely, a low ratio is easy to spin up but may limit your top speed on flat ground. Our fixed gear gear ratio calculator helps you find the perfect balance.

Fixed Gear Gear Ratio Formula and Explanation

The core calculation is simple, but its implications are complex. Our fixed gear gear ratio calculator handles the math for you, but understanding the formulas provides deeper insight into your bike’s performance.

1. Gear Ratio: The primary value. It’s calculated as: Gear Ratio = Chainring Teeth / Cog Teeth.
2. Skid Patches: This determines how many distinct points on your rear tire make contact with the ground when you skid to a stop. More patches mean more even tire wear. It’s found by simplifying the fraction of Chainring/Cog and looking at the denominator. An ambidextrous skidder can sometimes double this number.
3. Gain Ratio: A more comprehensive metric than gear inches, it relates the distance the bike travels to the distance the pedal travels, accounting for crank arm length. The formula is: Gain Ratio = (Wheel Radius / Crank Length) * Gear Ratio.
4. Rollout: This is the actual distance the bike travels forward with one full pedal revolution, measured in meters or feet. The formula is: Rollout = Gear Ratio * Wheel Circumference.

Variable Explanations

Variable	Meaning	Unit	Typical Range
Chainring Teeth	Number of teeth on the front sprocket	Teeth	42 – 55
Cog Teeth	Number of teeth on the rear sprocket	Teeth	13 – 22
Wheel Circumference	Total distance around the tire	mm	2000 – 2200
Crank Length	Length of the pedal crank arm	mm	165 – 175

Practical Examples

Using a fixed gear gear ratio calculator is best understood with real-world scenarios.

Example 1: The City Commuter

• Inputs: Chainring = 46t, Cog = 17t, Wheel = 700x28c, Crank = 170mm
• Calculator Results:
  • Gear Ratio: 2.71
  • Skid Patches: 17
  • Gain Ratio: 5.4
  • Rollout: 5.84 meters
• Interpretation: This is a great all-around ratio. The 2.71 gear ratio is easy to accelerate from traffic lights, and the 17 skid patches (a prime number cog is great for this) ensure the rear tire wears very slowly. The rollout is moderate, allowing for a decent cruising speed without frantic pedaling.

Example 2: The Track Racer

• Inputs: Chainring = 50t, Cog = 15t, Wheel = 700x23c, Crank = 165mm
• Calculator Results:
  • Gear Ratio: 3.33
  • Skid Patches: 3
  • Gain Ratio: 7.0
  • Rollout: 7.04 meters
• Interpretation: This is a high-performance setup. The 3.33 gear ratio provides a massive rollout for high speeds on the velodrome. However, the 3 skid patches (50 and 15 share a common divisor of 5) mean the tire will wear out very quickly in specific spots if used for skidding. This setup prioritizes speed over tire longevity, which is perfect for its intended use. Using a fixed gear gear ratio calculator confirms this is a specialized choice.

How to Use This Fixed Gear Gear Ratio Calculator

Our fixed gear gear ratio calculator is designed for ease of use and detailed analysis.

1. Enter Your Components: Start by inputting the number of teeth on your chainring and rear cog. These are the most critical values.
2. Specify Wheel and Crank Size: For accurate Rollout and Gain Ratio calculations, select your wheel/tire size and enter your crank arm length. Default values are provided for common setups.
3. Indicate Skid Style: Let the calculator know if you can skid with either foot forward. This affects the skid patch calculation.
4. Analyze the Results: The calculator instantly updates. The Gear Ratio is your primary result. Use the intermediate results—Skid Patches, Gain Ratio, and Rollout—to understand the complete performance profile.
5. Consult the Charts: Use the dynamic speed table and comparison chart to see how your setup performs at different speeds and against alternative cog choices. This is key to making an informed decision beyond the raw numbers from the fixed gear gear ratio calculator.

Key Factors That Affect Fixed Gear Ratio Choice

Choosing a gear ratio isn’t just about plugging numbers into a fixed gear gear ratio calculator. Several factors influence the right choice for you.

• Terrain: If you live in a hilly area, a lower gear ratio (e.g., 2.5-2.8) is crucial for manageable climbs. For flat cities, a higher ratio (2.8-3.2) is more efficient.
• Riding Style: Do you prioritize quick acceleration (lower ratio) or high top speed (higher ratio)? Do you perform skids and tricks (prioritize high skid patch count)?
• Physical Strength and Fitness: A stronger rider can push a higher gear ratio more comfortably. Newer riders should start with a more moderate ratio to avoid knee strain.
• Cadence Preference: Do you prefer to “spin” with a high cadence or “mash” with a lower cadence? Your gear ratio directly controls your cadence at any given speed.
• Desired Top Speed vs. Acceleration: There is always a trade-off. A high gear ratio is fast but slow to get moving. A low gear ratio is quick off the line but tops out early. The fixed gear gear ratio calculator helps quantify this trade-off.
• Tire Longevity: If you skid frequently, choosing a chainring/cog combination that yields a high number of skid patches will save you a lot of money on tires. Prime-numbered cogs (like 13, 17, 19) are excellent for this.

Frequently Asked Questions (FAQ)

1. What is a good beginner gear ratio?

A ratio around 2.7 to 2.8 (like 46/17 or 48/17) is an excellent starting point. It offers a good balance of acceleration and top speed and is manageable in most urban environments. Use our fixed gear gear ratio calculator to explore options around this range.

2. Why are skid patches important?

When you skid on a fixed gear, your cranks are always in the same position (usually horizontal). This means the same spot(s) on the tire contact the ground. A low number of skid patches (e.g., 1 or 2) will wear out your tire extremely quickly. A high number (e.g., 15+) distributes the wear evenly, dramatically increasing tire life.

3. What’s the difference between gear ratio and gain ratio?

Gear ratio is a simple comparison of chainring to cog. Gain ratio is a more advanced metric that also includes wheel size and crank length, giving a true measure of mechanical advantage. It represents how far the bike moves for every unit of distance the pedal travels.

4. Can I use this fixed gear gear ratio calculator for a single-speed bike?

Yes! The calculations for Gear Ratio, Gain Ratio, and Rollout are identical for single-speed freewheel bikes. The only metric that doesn’t apply is skid patches, as you cannot skid with a freewheel.

5. How do I find out my chainring and cog teeth count?

The number of teeth is almost always stamped directly onto the component. Look for a number like “48T” on the chainring and “17T” on the cog.

6. Why do prime numbers for cogs give more skid patches?

A prime number cog (like 17) is less likely to share a common divisor with your chainring number. The calculation for skid patches involves reducing the chainring/cog fraction. When the denominator is a prime number, the fraction often can’t be reduced, resulting in the maximum number of skid patches.

7. Is a higher rollout always better?

Not necessarily. A higher rollout means more distance per pedal stroke, which translates to a higher potential speed. However, it also means it’s harder to get started and to climb hills. The “best” rollout depends on your strength and where you ride. A fixed gear gear ratio calculator helps you find your personal sweet spot.

8. What does it mean to be an “ambidextrous skidder”?

This refers to a rider who is skilled enough to initiate a skid with either their left foot or right foot forward. In certain gear ratios, this ability can double the number of available skid patches, further extending tire life.