7 reference tools
Gear Calculators: Ratio, Module, Dimensions & Forces
Calculate gear ratio, module and diametral pitch, spur gear dimensions, center distance, mesh forces, backlash, and simple planetary speeds.
Which gear calculator should you use?
Start with the quantity you need: ratio for speed, module or diametral pitch for tooth size, center distance for nominal mounting geometry, and mesh force for a known torque. Use the planetary tool for a simple sun–ring–carrier arrangement. The spur-gear tools describe their own geometry assumptions; matching a numerical result alone does not establish a compatible or adequately rated gear pair.
Choose a calculator
- #001
Gear Center Distance Calculator
Calculate the nominal center distance, pitch diameters, and ratio of two standard external spur gears from module and tooth counts.
- #002
Gear Module / Diametral Pitch Converter
Convert gear module and diametral pitch in either direction, with equivalent metric and imperial circular pitch values, formulas, and engineering scope notes.
- #003
Gear Ratio Calculator
Calculate gear ratio, driven RPM, speed reduction or overdrive, and rotation direction for one external spur-gear pair.
- #005
Spur Gear Dimensions Calculator
Use this spur gear calculator to find pitch, outside, root, and base diameters from module or diametral pitch, tooth count, and pressure angle.
- #006
Gear Mesh Force Calculator
Calculate spur gear tangential, radial, normal, and axial mesh forces from torque, operating pitch diameter, and pressure angle.
- #007
Gear Backlash Calculator
Calculate spur gear circular, normal, and angular backlash from center-distance increase, or find the equivalent center-distance change.
- #008
Planetary Gear Ratio Calculator
Calculate simple planetary gear ratio, output RPM, direction, planet teeth, and equal-spacing phasing for sun, ring, or carrier configurations.
Before you use the result
- Identify the gear arrangement first. The external-pair ratio and spur-geometry tools do not cover every helical, bevel, worm, or compound gear train.
- Keep module, diametral pitch, pressure angle, and pitch diameter on the same reference system. A unit conversion does not convert normal helical geometry into transverse geometry.
- After a speed or geometry calculation, check the relevant tooth-strength, tolerance, lubrication, shaft, and bearing requirements separately.
Each linked tool includes its own formulas, worked examples, input units, limitations, and source notes. See how MechClarity documents and checks its calculations.
Continue with related calculations
- Power, Torque & RPM Calculator and Drive Tools — Convert between shaft power, torque, and rotational speed in SI or imperial units, then continue to gear, pulley, shaft, and bearing calculations.
- Shaft Calculators: Stress, Deflection & Critical Speed — Calculate shaft torsion, diameter, bending stress, bearing reactions, deflection, critical speed, key stress, and rigid flange coupling loads.
- Bearing Calculators: L10 Life, Loads & Static Safety — Calculate bearing L10 life, equivalent dynamic and static loads, required dynamic rating, static safety factor, and variable-duty equivalent load.