Gear Ratio Calculator - RPM, Torque & Speed with Animated Gear Visualizer
Enter the tooth counts and input RPM for any two meshing gears. Instantly calculates gear ratio, output RPM, and torque multiplier - with a live animated gear diagram.
Data Privacy & Security
100% Local Processing. All calculations run entirely in your browser. No data is transmitted to external servers.
Gear Parameters
How to Use the Gear Ratio Calculator
- Enter the number of teeth on the Driver (input) gear — the gear powered by your motor or engine.
- Enter the number of teeth on the Driven (output) gear — the gear connected to your load.
- Enter the input shaft RPM from your motor or engine specifications.
- Optionally enter input torque to calculate the output torque after the gear reduction.
Gear Ratio Formula
Frequently Asked Questions
What is gear ratio?
Gear ratio is the ratio of the number of teeth on the driven gear to the number of teeth on the driver gear. A gear ratio of 3:1 means the output shaft rotates once for every 3 rotations of the input shaft, tripling the torque while reducing speed by a factor of 3.
How is gear ratio calculated?
Gear ratio = Number of teeth on driven gear ÷ Number of teeth on driver gear. Alternatively, gear ratio = Input RPM ÷ Output RPM. A larger driven gear relative to the driver produces a higher gear ratio (more torque, less speed).
What is the difference between gear reduction and overdrive?
Gear reduction (ratio > 1) occurs when the driven gear has more teeth than the driver, resulting in lower output speed but higher torque. Overdrive (ratio < 1) occurs when the driven gear has fewer teeth, producing higher output speed but lower torque.
How does gear ratio affect torque?
Torque is multiplied by the gear ratio. If the gear ratio is 4:1, the output torque is 4 times the input torque (minus mechanical losses from friction). This mechanical advantage is why gear reductions are used in heavy machinery and electric vehicles.
How do I calculate output RPM from gear ratio?
Output RPM = Input RPM ÷ Gear Ratio. For example, with an input of 1800 RPM and a gear ratio of 3:1, Output RPM = 1800 ÷ 3 = 600 RPM.
Does this calculator work for sprockets and pulleys?
Yes. The gear ratio formula applies equally to sprockets (chain drives) and pulleys (belt drives). For sprockets, use tooth count directly. For smooth pulleys, use diameter ratio instead of tooth count — the math is identical.
What is a compound gear train?
A compound gear train uses multiple gear pairs in series, where the total gear ratio is the product of the individual stage ratios. For example, two stages of 3:1 each produce a total ratio of 9:1. This calculator handles single-stage calculations; multiply ratios for compound trains.
What gear ratio do I need for my application?
Required ratio = Input RPM ÷ Target Output RPM. For example, to reduce a 3600 RPM motor to 1200 RPM, you need a 3:1 gear ratio. This means your driven gear should have 3× more teeth than your driver gear.
Limitations
This calculator assumes an ideal gear mesh with 100% mechanical efficiency. Real-world gear systems have efficiency losses (typically 95–98% per stage for spur gears) due to friction and lubrication. For precision drivetrain design, account for efficiency losses when calculating actual output torque and power.
Data Privacy & Security
This Gear Ratio Calculator runs entirely in your web browser. No gear specifications or design parameters are sent to any external server, ensuring complete privacy for your mechanical engineering projects.
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