Enter Frequency
Formula
λ = v / f = (c × velocity factor) / frequency
In free space, the velocity factor is 1. Cables and other materials slow the wave, so their velocity factor is less than 1.
Worked Example
At 100 MHz in free space:
λ = 299,792,458 / 100,000,000 = 2.998 m
The wave is about 9.84 feet long. Antenna elements are often designed as a fraction of this length.
Assumptions and Limits
This is a phase-velocity calculation. For coaxial cable, use the manufacturer's velocity factor. For PCB transmission lines, the effective dielectric constant determines the actual velocity.
A calculated wavelength is a starting point. Nearby materials, conductor diameter, insulation, antenna end effects, and construction details change practical dimensions.