What is a gear ratio calculator?
A simple external gear pair trades rotational speed for torque according to the tooth-count ratio. This calculator treats the driving gear as the input and the driven gear as the output.
For a connected mechanics or engineering question, compare this result with the Torque Calculator rather than treating one formula as a complete model.
How does the gear ratio calculator work?
The gear ratio is driven teeth divided by driving teeth. Output RPM is input RPM divided by that ratio, while the ideal torque multiplication equals the ratio before friction and other losses.
If your next step involves another quantity, the Engine Horsepower Calculator provides a separate calculation with its own units and assumptions.
What formula does the gear ratio calculator use?
The calculator first converts the entered values to a consistent working unit system, then applies the standard relationship shown below. The displayed converted values make the calculation easier to check.
Use the unit selectors beside the inputs rather than adding unit symbols to number fields. Small differences from another source can occur because of rounding, constants, or different modeling assumptions.
How do you use this gear ratio calculator?
- Enter the requested numeric values.
- Choose the correct units or solve-for option where shown.
- Select Calculate Gear Ratio.
- Read the main result, converted values, and method note.
- Use Copy, Download, or Print when you need to keep the result; select Reset to start over.
If you edit an input after calculating, the previous result is cleared so an old value is not mistaken for a current one.
What do the gear ratio results mean?
A ratio above 1 reduces output speed and ideally multiplies torque. A ratio below 1 increases output speed and reduces ideal output torque. A ratio of 1 keeps speed magnitude unchanged.
For a useful cross-check or conversion, open the Tire Size Calculator; it can help translate this result into a related planning value.
What are the limitations of this gear ratio calculator?
This is an ideal single-stage tooth-count model. It ignores efficiency losses, gear geometry, backlash, tooth strength, idlers, planetary arrangements, and multi-stage drivetrains.
You can also browse the Automotive Calculators when the problem extends beyond this equation.
Who should use this gear ratio calculator?
This gear ratio calculator is useful for students, instructors, technicians, makers, and anyone who needs a quick transparent check of the standard relationship used by this tool. It is best suited to educational work, planning, estimation, homework checks, and non-safety-critical technical calculations.
For related problems, browse the Physics & Engineering Calculators category. For professional or regulated work, use the applicable engineering standards, manufacturer data, measured conditions, and qualified review instead of relying on a general-purpose calculator alone.
Frequently asked questions
Sources and methodology
The formula, unit conventions, and cautions on this page are documented so the calculation can be checked against authoritative references.