The virtual number of teeth in a bevel gear is a concept used to characterize the geometry of bevel gears. Unlike spur gears, which have a constant pitch diameter, bevel gears have varying pitch diameters along their teeth. The virtual number of teeth is an imaginary parameter that helps express the equivalent engagement characteristics of a bevel gear in a way that is comparable to a spur gear.

In a bevel gear, the tooth profile is curved, and the pitch diameter changes along the tooth height. The virtual number of teeth is determined by considering the equivalent spur gear that would have the same pitch diameter and provide similar tooth engagement characteristics. It is a theoretical value that simplifies the analysis and design of bevel gears.

The concept of virtual number of teeth is particularly useful in calculations related to the design, manufacturing, and analysis of bevel gears. It allows engineers to apply familiar formulas and methods used for spur gears to bevel gears, making the design process more straightforward.