A spur gear is a cylindrical gear with straight teeth parallel to the shaft axis. Driver and driven tooth counts set gear ratio and speed change, while module or diametral pitch determines pitch diameter, outside diameter, centre distance, circular pitch, and pitch-line velocity for a compatible pair.
Spur Gear Calculator applies this concept to its defined inputs and workflow. It can be used as a local spur gear calculator to plan a basic external spur gear pair before detailed strength, backlash, contact ratio, lubrication, or supplier review.
The calculator evaluates single gear geometry, gear pair center distance, gear ratio from teeth, and pitch-line velocity estimate and returns gear ratio, center distance, pitch diameters, and outside diameters using the stated method. The selected units and sign or reference conventions must describe one consistent physical case. Users should interpret the output within the assumptions shown on the page and repeat the check with trusted reference values when the result affects engineering or research decisions. No gear strength, tooth contact, backlash, interference, noise, lubrication, material, or heat-treatment analysis is included.