Waveguide Mode Calculator

Calculate cutoff frequencies for TE and TM modes in rectangular and circular waveguides.

What is a waveguide?

A waveguide is a hollow metal tube that guides RF signals like a water slide guides water. Unlike a wire or coax cable, signals travel through the air inside the tube — and only certain wave patterns (called “modes”) can fit inside based on the tube's dimensions.

Why it matters: Radar dishes on ships use waveguides to carry powerful microwave signals with near-zero loss. The cutoff frequency tells you the lowest frequency that can pass through — below it, the signal is blocked entirely.

Parameters
Rectangular waveguide cross-section dimensions.

The wider inner dimension of the tube. Larger = lower cutoff frequency. WR-90 standard: 22.86 mm.

The narrower inner dimension. Usually half the width. WR-90 standard: 10.16 mm.

Air = 1.0 (most waveguides). Use a higher value only if the guide is filled with a dielectric material.

Cutoff Frequencies
First 12 modes sorted by cutoff frequency. TE10 is dominant.
TE10dominant
6.562 GHz
TE20
13.123 GHz
TE01
14.764 GHz
TE11
16.156 GHz
TE30
19.685 GHz
TE21
19.753 GHz
TE31
24.606 GHz
TE40
26.247 GHz
TE02
29.528 GHz
TE41
30.114 GHz
TE12
30.248 GHz
TE22
32.313 GHz

The dominant mode TE10 has the lowest cutoff frequency. Typical waveguide operation is from 1.25× to 1.9× the dominant mode cutoff to avoid higher-order modes.