Fixed Gear Gear Ratio Calculator
Instantly calculate your gear ratio, gear inches, gain ratio, and skid patches to perfectly tune your fixed gear or track bike performance.
Your Fixed Gear Metrics
What is a Fixed Gear Gear Ratio?
A fixed gear gear ratio is the fundamental number that defines how a fixed gear or single-speed bike feels and performs. It represents the ratio 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 single number dictates how many times the rear wheel rotates for every full rotation of the pedals.
Understanding and choosing the right gear ratio is critical for any fixed gear rider. A “high” gear ratio (e.g., 3.0) requires more effort to pedal but results in higher top speeds. A “low” gear ratio (e.g., 2.5) is easier to pedal, making it ideal for climbing hills and quick acceleration, but limits top speed. This fixed gear gear ratio calculator is an essential tool for urban cyclists, track racers, and couriers who need to fine-tune their ride.
The Fixed Gear Gear Ratio Formula and Explanation
While the primary gear ratio is simple, several other metrics provide a deeper understanding of your setup. Our calculator computes them all for you. The core formula is:
Gear Ratio = Number of Chainring Teeth / Number of Cog Teeth
This tells you the raw mechanical advantage. To understand how that translates to the road, we use other metrics like Gear Inches and Gain Ratio. Check out our track bike setup guide for more details.
Key Metrics Table
| Variable / Metric | Meaning | Unit | Typical Range |
|---|---|---|---|
| Chainring Teeth | Number of teeth on the front sprocket. | Teeth (unitless) | 42 – 55 |
| Cog Teeth | Number of teeth on the rear sprocket. | Teeth (unitless) | 13 – 22 |
| Gear Ratio | How many times the wheel turns for one pedal revolution. | Ratio (unitless) | 2.0 – 3.5 |
| Gear Inches | The effective wheel diameter, relating ratio to speed potential. | Inches | 60 – 100 |
| Gain Ratio | The most complete metric, relating pedal travel to distance traveled. Learn more in our article explaining gain ratio. | Ratio (unitless) | 4.0 – 8.0 |
| Skid Patches | The number of distinct wear spots on your rear tire from skidding. | Count (unitless) | 1 – 22 |
Practical Examples
Let’s see how the fixed gear gear ratio calculator works with some common setups.
Example 1: The All-Rounder Urban Setup
- Inputs: 46t Chainring, 17t Cog, 672mm Tire (700x25c), 165mm Cranks
- Results:
- Gear Ratio: 2.71
- Gear Inches: 71.3
- Gain Ratio: 5.48
- Skid Patches: 17
- Interpretation: This is a fantastic, versatile setup for city riding. It provides a good balance between acceleration from a standstill and a comfortable top speed. The 17 skid patches ensure very even tire wear.
Example 2: The Fast Track / Messenger Setup
- Inputs: 49t Chainring, 15t Cog, 668mm Tire (700x23c), 170mm Cranks
- Results:
- Gear Ratio: 3.27
- Gear Inches: 85.9
- Gain Ratio: 6.42
- Skid Patches: 15
- Interpretation: This is a much harder gear. It’s difficult to get moving but allows for very high speeds on flat ground, making it suitable for track racing or experienced messengers. The 15 skid patches offer good tire longevity.
How to Use This Fixed Gear Gear Ratio Calculator
Using our tool is straightforward. Follow these steps for an accurate analysis of your setup:
- Enter Chainring Teeth: Count the teeth on your front chainring and enter the number.
- Enter Cog Teeth: Do the same for your rear cog.
- Enter Tire Diameter: This is crucial for accurate Gear Inch and Gain Ratio calculations. If you’re unsure, measure from the ground to the top of your inflated tire in millimeters. Use our helper text for common sizes.
- Enter Crank Arm Length: This is usually printed on the inside of the crank arm. Enter it in millimeters.
- Analyze Your Results: The calculator instantly updates your Gear Ratio, Gear Inches, Gain Ratio, and Skid Patches. Use these metrics to decide if the combination is right for your riding style. Our general bike gear calculator can provide further context.
Key Factors That Affect Your Fixed Gear Ratio Choice
Choosing a gear ratio isn’t just about a single number. Several factors influence the ideal setup, which this fixed gear gear ratio calculator helps you navigate.
- 1. Terrain:
- Are you riding on flat ground or in a hilly city? Flatter areas allow for higher gear ratios, while hills demand lower, easier ratios for climbing.
- 2. Riding Style:
- Do you prefer quick acceleration and sprinting (lower ratio) or maintaining high speeds over long distances (higher ratio)?
- 3. Rider Strength and Fitness:
- A stronger rider can handle a higher gear ratio more effectively. Don’t over-gear yourself, as it can lead to knee strain.
- 4. Brakeless Riding and Skid Patches:
- If you ride brakeless, maximizing skid patches is crucial for tire life. A prime number cog (like 13, 17, 19) paired with a chainring it doesn’t share factors with is ideal. Our fixed gear skid patch calculator focuses specifically on this.
- 5. Crank Arm Length:
- Shorter cranks (like 165mm) are common on track bikes to improve cornering clearance and encourage a higher cadence. This affects the Gain Ratio, which is a measure of leverage.
- 6. Wheel and Tire Size:
- A larger effective wheel diameter (from a fatter tire) will slightly increase your final drive ratio, making the gear feel harder. This is accurately reflected in the Gear Inches and Gain Ratio metrics.
Frequently Asked Questions (FAQ)
A good starting point is a gear ratio between 2.7 and 2.8, such as a 46×17 or 48×17. This provides a manageable balance for learning to control a fixed gear bike without being too difficult to pedal.
If you ride brakeless and stop by skidding, skid patches represent the number of different spots on your tire that will contact the ground during a skid. More patches mean wear is distributed more evenly, and your tire lasts much longer. A low number (e.g., 1) means you will wear through one spot very quickly.
Gear Ratio is a simple mechanical ratio. Gain Ratio is a more complete metric created by Sheldon Brown that accounts for wheel size AND crank arm length. It represents the meters traveled for every meter the pedal travels in a circle, providing a true measure of leverage.
Use a cog with a prime number of teeth (e.g., 17) and a chainring that is not a simple multiple of that cog. For example, 48×16 gives you only 1 skid patch, while 48×17 gives you 17.
Yes, absolutely. The Gear Ratio, Gear Inches, and Gain Ratio calculations are identical for any single-speed bicycle. The “Skid Patches” metric is only relevant for fixed-gear riders.
It’s a traditional way to compare gear ratios. It represents the diameter of the main wheel of a penny-farthing bicycle that would have the same gear. A higher number means a “harder” gear and higher speed potential.
Yes. A ratio that is too high for your strength and terrain will be very difficult to start, accelerate, and climb with. It can also put excessive strain on your knees.
This happens when your chainring and cog share a common divisor. For example, a 48t chainring and 16t cog have a gear ratio of exactly 3 (48/16). Their greatest common divisor is 16. The formula for skid patches is Cog / GCD, so 16 / 16 = 1 skid patch, which is very bad for tire wear.