Understand Your Bike's Gears

Explore gear ratios, cadence, and power in one interactive tool. No magic. Just physics.

Open Gearing Calculator

Why This Calculator?

Learn the Math

Gear ratios aren't magic. See exactly how chainring teeth, cog teeth, and wheel size work together to determine your speed and cadence.

Compare Setups

Test different drivetrains before you buy. Road compact vs. standard? Gravel 1x vs. 2x? See the real differences.

Understand Power

Calculate the watts you need to climb a hill or maintain a given speed. Includes rolling resistance and aerodynamic drag.

Private by Design

All calculations run in your browser. No accounts, no ads, no inputs sent to a server. The site uses Cloudflare Web Analytics for aggregate, cookieless traffic counts.

How It Works

  1. Choose your bike setup: Select a drivetrain preset (road compact, gravel, MTB) or enter custom chainring and cog sizes.
  2. Pick an active mode: Speed, cadence, or grade. This is what you control; the others calculate automatically.
  3. Adjust your input: Change speed, pedaling rate, or hill grade. See cadence, speed, and power update in real time.
  4. Understand the results: Development, gear ratio, and power required tell you how your bike responds.

Frequently Asked Questions

What is development?

Development is the distance your bike travels with one complete pedal revolution. It combines wheel circumference and gear ratio: development = wheel circumference × gear ratio. Larger development means faster speed at the same cadence, but harder pedaling.

What's the difference between road compact and road standard?

Road compact (50/34T) has a smaller low gear, making climbing easier on steep hills. Road standard (53/39T) has a higher gear range, useful for flat terrain and long descents. Most riders choose compact for versatility.

How accurate is the power calculation?

The power model estimates watts based on rolling resistance, aerodynamic drag, and gravitational climbing force. Real power depends on rider efficiency, tire pressure, wind, and pavement smoothness. Use this as an estimate for comparing setups, not as a precise measurement.

Can I export my setup?

Yes. Use the "Copy Share Link" button to save your exact setup (chainring, cog, weight, etc.) as a URL. Share it with friends or bookmark your favorite configurations.

What wheel sizes are supported?

The calculator includes common sizes: 20", 24", 26" MTB, 27.5" MTB, 28" road, and 29" MTB. You can also enter a custom wheel circumference in meters.

Is this compatible with e-bikes?

The gearing calculations work for any bike. Power calculation is for human watts only—it doesn't account for motor assistance. For e-bikes, use this to understand the drivetrain, not total system power.

Who built this?

Bikes Explained is an open-source project built to help cyclists understand their machines. All code is on GitHub. No ads, no tracking, no business model. Just education.

Ready to Explore?

Open the calculator and start experimenting with your bike's gearing.

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