Cycle Calculator

by

Bicycle Gear Ratio & Rollout Calculator

(e.g., 2096 for 700x23c, 2133 for 700x28c, 2070 for 26×1.75)

Calculation Results:

Gear Ratio: –

Gear Inches: –

Rollout (meters per pedal revolution): –

function calculateGearRatio() { var chainringTeeth = parseFloat(document.getElementById("chainringTeeth").value); var cassetteCogTeeth = parseFloat(document.getElementById("cassetteCogTeeth").value); var wheelCircumferenceMM = parseFloat(document.getElementById("wheelCircumferenceMM").value); if (isNaN(chainringTeeth) || chainringTeeth <= 0) { alert("Please enter a valid number for Chainring Teeth."); return; } if (isNaN(cassetteCogTeeth) || cassetteCogTeeth <= 0) { alert("Please enter a valid number for Cassette Cog Teeth."); return; } if (isNaN(wheelCircumferenceMM) || wheelCircumferenceMM <= 0) { alert("Please enter a valid number for Wheel Circumference (mm)."); return; } var gearRatio = chainringTeeth / cassetteCogTeeth; var gearInches = gearRatio * (wheelCircumferenceMM / 25.4); // Convert mm to inches (1 inch = 25.4 mm) var rolloutMeters = gearRatio * (wheelCircumferenceMM / 1000); // Convert mm to meters document.getElementById("gearRatioResult").innerText = gearRatio.toFixed(2); document.getElementById("gearInchesResult").innerText = gearInches.toFixed(1) + " inches"; document.getElementById("rolloutMetersResult").innerText = rolloutMeters.toFixed(2) + " meters"; }

Understanding Your Bicycle's Gear Ratios and Rollout

For any cyclist, understanding how your bicycle's gearing works is crucial for optimizing performance, comfort, and efficiency. Whether you're climbing steep hills, cruising on flat roads, or sprinting for the finish line, the right gear combination makes all the difference. This Bicycle Gear Ratio & Rollout Calculator helps you quantify your bike's capabilities.

What is Gear Ratio?

The gear ratio is a fundamental metric that describes the mechanical advantage of your drivetrain. It's calculated by dividing the number of teeth on your front chainring by the number of teeth on your rear cassette cog. A higher gear ratio means you travel further with each pedal revolution, requiring more effort but allowing for higher speeds. A lower gear ratio makes pedaling easier, ideal for climbing or starting from a stop, but results in slower speeds for the same cadence.

For example, a 50-tooth chainring paired with an 11-tooth cog (50/11) gives a gear ratio of approximately 4.55. This is a "tall" or high gear, suitable for speed. A 34-tooth chainring with a 28-tooth cog (34/28) yields a ratio of about 1.21, a "short" or low gear, perfect for steep ascents.

What are Gear Inches?

Gear inches provide a more intuitive way to understand your gearing by relating the gear ratio to the size of your wheel. It represents the diameter of a direct-drive wheel (like a penny-farthing) that would travel the same distance per pedal revolution as your current gear combination. The formula is: (Chainring Teeth / Cassette Cog Teeth) * Wheel Diameter (in inches).

A larger gear inch value indicates a harder gear, while a smaller value signifies an easier gear. This metric is particularly useful for comparing gearing across different wheel sizes (e.g., 26-inch mountain bikes vs. 700c road bikes) because it normalizes the effect of wheel size.

Using our example of a 50/11 gear ratio on a 700c wheel (approx. 27.5 inches diameter, or 2096mm circumference), the gear inches would be around 100.0 inches. This means one pedal revolution moves you as far as a 100-inch diameter wheel would in one revolution.

What is Rollout (Meters per Pedal Revolution)?

Rollout is another practical metric, especially for track cyclists or those who prefer metric measurements. It tells you the actual distance your bicycle travels forward with one complete revolution of the pedals. The calculation is: (Chainring Teeth / Cassette Cog Teeth) * Wheel Circumference (in meters).

This value directly indicates how much ground you cover with each pedal stroke. A higher rollout means more distance per stroke, suitable for speed, while a lower rollout means less distance, making it easier to accelerate or climb. It's a direct measure of how "long" or "short" your gear is in terms of distance covered.

For the 50/11 gear ratio with a 700c wheel (2096mm circumference, or 2.096 meters), the rollout would be approximately 9.53 meters per pedal revolution. This means every time you complete a full pedal stroke, your bike moves over 9.5 meters forward.

How to Use This Calculator:

  1. Chainring Teeth: Enter the number of teeth on your front chainring. If you have multiple chainrings, choose the one you want to analyze.
  2. Cassette Cog Teeth: Enter the number of teeth on the specific rear cog you are interested in. Your cassette will have a range of cogs (e.g., 11-28t).
  3. Wheel Circumference (mm): Input the measured circumference of your wheel with the tire inflated. This is the most accurate method. Common values are provided as examples, but measuring your specific wheel and tire combination is best.
  4. Click "Calculate Gear Metrics" to see your gear ratio, gear inches, and rollout.

By experimenting with different chainring and cog combinations, you can better understand your bike's gearing and make informed decisions about component upgrades or simply choose the optimal gear for your next ride.

Leave a Comment