Wavelength & Frequency Calculator
Convert frequency to wavelength for sound in air or water, light and radio in a vacuum, or any wave speed you enter.
How long each wave is, from its frequency and how fast it travels.
How the wavelength & frequency calculator works
Wave speed equals frequency times wavelength, so λ = v ÷ f. Sound at 440 Hz (concert A) has a wavelength of 78 cm in air but 3.4 m in water, because sound travels faster there; a 100 MHz FM radio wave is 3 m long; visible light is 400–700 nanometers. Pick the medium or enter a speed.
The period — the time for one cycle — is simply 1 ÷ f.
Formula: λ = v ÷ f · T = 1 ÷ f
Worked examples
| Inputs | Wavelength | Note |
|---|---|---|
| 440 Hz in air | 0.779545 m | 78 cm — concert A |
| 100 MHz FM radio | 2.997925 m | 3.0 m |
| 2.4 GHz Wi-Fi | 0.124914 m | 12.5 cm |
| 440 Hz in water | 3.363636 m | 3.36 m |
FAQFrequently asked questions
Why is the same note a longer wave in water?
Because sound travels faster in water (about 1,480 m/s versus 343 in air) and wavelength is speed divided by frequency.
What wavelength is visible light?
About 380 nm (violet) to 750 nm (red). Green is around 550 nm — a frequency of 545 THz.
How long is a 50 Hz mains wave?
In a vacuum, 6,000 km — which is why power grids are treated as circuits, not transmission lines.
Why does antenna size relate to wavelength?
Efficient antennas are a simple fraction of the wavelength — a half-wave dipole for 100 MHz FM is about 1.5 m; for 2.4 GHz Wi-Fi about 6 cm.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Institute of Standards and Technology — the US measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.