Frequency and wavelength calculator
Every wave — radio, light, sound — has a frequency and a wavelength, and the two are tied together by how fast the wave travels. This calculator converts between them: enter a frequency to get the wavelength, or a wavelength to get the frequency. It is handy for antenna sizing, optics, acoustics and physics study.
How it works
Frequency (f), wavelength (λ) and wave speed (v) obey one relationship:
v = f × λ, so λ = v / f and f = v / λ
Choose what to solve for and the tool rearranges the formula accordingly. The default wave speed is the exact speed of light, 299,792,458 m/s, correct for radio waves and light in a vacuum. For sound in air at room temperature, change it to about 343 m/s. Frequency is entered in MHz and wavelength in metres.
Example
For a 100 MHz FM signal (100 × 10⁶ Hz) travelling at the speed of light:
λ = 299,792,458 ÷ 100,000,000 ≈ 3 metres.
Conversely, a 0.5 m wavelength at the speed of light corresponds to f = 299,792,458 ÷ 0.5 ≈ 600 MHz.
| Wave | Speed used | Note |
|---|---|---|
| Radio / light (vacuum) | 299,792,458 m/s | default |
| Sound in air (≈20 °C) | 343 m/s | acoustics |
| Light in a medium | < c | use the medium’s speed |
Every calculation runs locally in your browser — no network requests.