Our gear ratio calculator helps engineers, mechanics, and hobbyists design and analyze gear systems. Calculate the ratio between driving and driven gears, determine output RPM and torque, and analyze compound gear trains. Essential for automotive transmissions, bicycles, robotics, and industrial machinery.
Choose to calculate ratio, find teeth, or analyze compound gears
Input the number of teeth on driving and driven gears
Enter input RPM and torque for output calculations
See gear ratio, output speed, and torque multiplication
Gear ratio is the ratio of driven gear teeth to driving gear teeth. A ratio greater than 1 reduces speed but increases torque (reduction gear). A ratio less than 1 increases speed but reduces torque (overdrive).
Gear Ratio = Driven Teeth ÷ Driving Teeth
Gear ratio > 1 = speed reduction, torque increase (most common)
Gear ratio < 1 = speed increase, torque reduction (overdrive)
Compound gear trains multiply individual ratios together
For chains/belts, use sprocket/pulley teeth or diameters
Efficiency losses: ~2% per gear mesh, ~3-5% for chains
Bicycle: larger rear sprocket = easier pedaling, lower speed
Car final drive ratios typically range from 2.5:1 to 4.5:1
Gear ratios are fundamental to nearly every mechanical system that transmits rotational motion — from bicycle drivetrains and automotive transmissions to industrial conveyors and robotic actuators. A gear ratio describes the relationship between a driving gear (input) and a driven gear (output), expressed as the number of teeth on the driven gear divided by the teeth on the driving gear. A ratio of 3:1 means the output shaft turns once for every three turns of the input shaft, but delivers three times the torque. This inverse relationship between speed and torque is what makes gears so versatile. In a typical 6-speed car transmission, first gear might have a ratio of 3.5:1 for maximum torque at low speed, while sixth gear drops to 0.75:1 for fuel-efficient highway cruising. Compound gear trains multiply individual ratios together, enabling enormous reductions — a worm gear set alone can achieve 60:1 in a single stage. Engineers, mechanics, and hobbyists working on go-karts, 3D printers, CNC machines, and robotics projects all need accurate gear ratio calculations to match motor output to the required load speed and torque.
Gear ratios determine how speed and torque are transferred between rotating shafts. A higher ratio means more torque but less speed, which is ideal for starting heavy loads. A lower ratio means more speed but less torque, which is ideal for high-speed operation.
Gear ratios are used in automotive transmissions, bicycles, industrial machinery, robotics, and power tools. Understanding ratios helps in selecting the right gears for your speed and torque requirements.
Data sourced from trusted institutions
All formulas verified against official standards.