Free frequency to wavelength converter. Convert hertz, kilohertz, megahertz, gigahertz, and terahertz — and instantly find the matching wavelength using the speed of light or speed of sound. Includes period and full-spectrum context.
Hz • kHz • MHz • GHz • nm • m
Uses the exact defined speed of light, c = 299,792,458 m/s, so wavelength results are physically precise.
Tells you which band a frequency belongs to — radio, microwave, infrared, visible light, and beyond.
All conversions run in your browser — no server, no account, nothing sent anywhere.
Frequency and wavelength are two ways of describing the same wave, linked by the wave's speed. The fundamental equation is v = f × λ, where v is the wave speed, f is frequency (in hertz), and λ (lambda) is wavelength. Because the speed is fixed for a given medium, frequency and wavelength are inversely proportional: as one goes up, the other goes down. For electromagnetic waves (light, radio, Wi-Fi) in a vacuum, the speed is the speed of light, c = 299,792,458 m/s. For sound in air at 20°C, it's about 343 m/s.
To find wavelength from frequency: λ = c ÷ f. A 100 MHz FM radio signal has a wavelength of 299,792,458 ÷ 100,000,000 = about 3 meters. A 2.4 GHz Wi-Fi signal is about 12.5 cm. Green light at 540 THz is about 555 nanometers. To find frequency from wavelength: f = c ÷ λ. The period — how long one full cycle takes — is simply T = 1 ÷ f.
The electromagnetic spectrum runs from low-frequency radio waves (long wavelengths, meters to kilometers) through microwaves, infrared, the narrow band of visible light (roughly 400–700 nm), then ultraviolet, X-rays, and gamma rays (extremely high frequency, tiny wavelengths). Sound is mechanical, not electromagnetic, so it travels far slower — which is why a 343 Hz sound wave has a 1-meter wavelength, while a 343 Hz radio wave would be nearly 875 kilometers long.
AM radio: ~1 MHz (~300 m). FM radio: ~100 MHz (~3 m). Wi-Fi: 2.4 GHz (12.5 cm) & 5 GHz (6 cm). 5G mid-band: 3.5 GHz (8.6 cm). Microwave oven: 2.45 GHz.
Violet: ~400 nm (750 THz). Blue: ~470 nm. Green: ~550 nm (540 THz). Yellow: ~580 nm. Red: ~700 nm (430 THz). Just beyond: UV (<400 nm), infrared (>700 nm).
At 343 m/s: 20 Hz (deep bass) = 17 m. 343 Hz = 1 m. Middle A (440 Hz) = 78 cm. 20 kHz (top of hearing) = 1.7 cm. Sound wavelengths are millions of times longer than light at the same frequency.
Period T = 1/f. A 1 Hz wave takes 1 second per cycle. 1 kHz = 1 ms. 1 MHz = 1 µs. 1 GHz = 1 ns. A 3 GHz CPU clock ticks once every 0.33 nanoseconds.