GearRatioSpeed
Calculate gear ratio and output speed from input and output gear teeth. Enter gear teeth and RPM to find gear ratio, speed ratio, and output rotational speed.
About This Calculator
The Gear Ratio Speed Calculator helps engineers, mechanics, students, and hobbyists determine the relationship between gear teeth counts and rotational speed in a two-gear system. By entering the number of teeth on your input (driving) gear and output (driven) gear, you can instantly calculate the gear ratio, speed ratio, and — when an input RPM is provided — the exact output rotational speed. This tool is essential for designing gear trains, transmissions, conveyor systems, and any mechanical power transmission application.
The calculator uses the fundamental gear relationship: gear ratio = output teeth / input teeth. Since meshing gears rotate one tooth at a time together, the speed ratio equals the gear ratio: output speed = input speed / gear ratio. If the input gear has 20 teeth and the output gear has 40 teeth, the gear ratio is 2:1, meaning the output rotates at half the input speed but delivers twice the torque. Conversely, a gear ratio of 0.5:1 (e.g., 40 input teeth and 20 output teeth) results in the output rotating twice as fast as the input — ideal for applications requiring speed increase, such as in bicycle drivetrains and certain industrial machinery.
How to Use
Simply enter the tooth count for both gears and optionally provide an input speed in RPM. The calculator instantly displays the gear ratio, speed ratio, and output speed. Results are presented with a detailed breakdown table and interactive bar and pie charts for easy visualization. The shareable URL lets you bookmark or share your specific gear configuration with colleagues or students.
Frequently Asked Questions
What is gear ratio speed?
Gear ratio speed refers to the relationship between the number of teeth on two meshing gears and how it affects rotational speed. The gear ratio is calculated as output teeth divided by input teeth, and the output speed equals input speed divided by this gear ratio.
How do you calculate gear ratio from teeth?
To calculate the gear ratio, divide the number of teeth on the output gear (driven gear) by the number of teeth on the input gear (driving gear). For example, if the input gear has 20 teeth and the output gear has 40 teeth, the gear ratio is 40/20 = 2.0, expressed as 2:1.
How does gear ratio affect rotational speed?
A gear ratio greater than 1 means the output gear has more teeth and rotates slower than the input gear. A gear ratio less than 1 means the output gear has fewer teeth and rotates faster. The relationship is: output speed = input speed / gear ratio.
What is the difference between gear ratio and speed ratio?
The gear ratio (output teeth / input teeth) and speed ratio (input speed / output speed) have the same numerical value. They describe the same relationship from different perspectives: gear ratio focuses on tooth counts, while speed ratio focuses on rotational speeds.
How do I calculate output RPM from gear ratio?
To calculate output RPM, divide the input RPM by the gear ratio. For example, with an input speed of 1000 RPM and a gear ratio of 2:1, the output speed is 1000 / 2 = 500 RPM. If the gear ratio is 0.5:1, the output speed would be 1000 / 0.5 = 2000 RPM.
What happens when the input gear has more teeth than the output gear?
When the input gear has more teeth than the output gear, the gear ratio is less than 1. This means the output gear rotates faster than the input gear — creating a speed increase. This configuration is called an overdrive and is common in vehicle transmissions for high-speed cruising.
What is a 2:1 gear ratio?
A 2:1 gear ratio means the output gear rotates once for every two rotations of the input gear. The output speed is half the input speed, but the output torque is doubled. This is typical in applications requiring speed reduction and torque multiplication, such as in conveyor systems and winches.
Is this gear ratio speed calculator free?
Yes, this gear ratio speed calculator is completely free to use with no registration or hidden charges. You can bookmark or share your calculation results via the shareable URL.