Wavelength & Frequency Calculator
Convert wavelength and frequency for light or sound, with photon energy.
About this tool
Choose the wave, light or radio in a vacuum, sound in air or water, light in glass or a custom speed, then enter either the frequency or the wavelength with its unit. The calculator gives the other value, the period and, for light and radio, the photon energy, the part of the electromagnetic spectrum and the visible colour.
How wavelength and frequency are related
For any wave, speed = frequency × wavelength, so λ = v ÷ f and f = v ÷ λ. Light and radio waves travel at c = 299,792,458 m/s in a vacuum. A 100 MHz FM station therefore has a wavelength of about 3 metres, Wi-Fi at 2.4 GHz about 12.5 cm, and green light at 550 nm a frequency of about 545 THz. Sound in air travels at only about 343 m/s at 20°C, so concert A at 440 Hz has a wavelength of about 78 cm. Light also comes in packets called photons, each with energy E = hf, where h is Planck's constant, 6.626 × 10⁻³⁴ J·s. A 550 nm photon carries about 3.6 × 10⁻¹⁹ J, or 2.25 electronvolts; ultraviolet photons carry more, which is why UV can damage skin and visible light can't. The electromagnetic spectrum runs from radio, through microwaves, infrared, visible light and ultraviolet, to X-rays and gamma rays. Honest limits: in a material such as glass or water, waves slow down and their wavelength shortens while the frequency stays the same, and band boundaries are conventions rather than sharp lines. The scientific calculator and the unit converter help with related calculations.
Frequently asked questions
What is the wavelength of 2.4 GHz Wi-Fi?
About 12.5 cm: 299,792,458 ÷ 2,400,000,000.
What frequency is visible light?
About 400 to 790 THz, which is wavelengths of roughly 750 nm (red) to 380 nm (violet).
How do you calculate photon energy?
E = hf, Planck's constant times frequency, or E = hc ÷ λ. Divide by 1.602 × 10⁻¹⁹ to convert joules to eV.
Is my data saved?
No. The calculation runs in your browser and nothing is stored or sent.