Gear Ratio Calculator
Calculate the ratio between a drive and driven gear. This free online automotive & vehicles calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
The gear ratio is the driven (output) gear's teeth divided by the drive (input) gear's teeth. A ratio above 1 is a reduction (more torque, lower speed); below 1 is an overdrive (higher speed, less torque). The same math applies to sprocket teeth or pulley diameters.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Drive Gear Teeth: 12
- Driven Gear Teeth: 42
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
Frequently Asked Questions
What does the Gear Ratio Calculator compute?
The Gear Ratio Calculator takes 2 input values and returns 3 results. Calculate the gear ratio between a driving and driven gear from their tooth counts, and see whether the pairing is an overdrive or a reduction.
Is my data sent to a server?
No. The Gear Ratio Calculator runs entirely in your browser using static JavaScript. Your inputs are never transmitted to CalculatorHive or any third party, and nothing is stored after you close the page.
Is this calculator free to use?
Yes. Every calculator on CalculatorHive is completely free. There is no signup, no paywall, and no usage limit. The site is supported by display advertising and affiliate partnerships, which are clearly labeled.
How accurate is the result?
The math is mathematically exact for the inputs you provide. Real-world accuracy depends on how accurately your inputs reflect the real situation — defaults are typical values, not guarantees.