Wavelength and Frequency Calculator

Written byOleh Soloninupdated 5 October 2026

Solve for

Medium

Wavelength

Frequency, Hz

Your own wave speed, m/s

Leave at 0 to use the medium's speed.

Result

Result599,584,900,000,000
What was calculatedFrequency, Hz
Frequency in readable units599.585 THz
Colour or bandgreen
Photon energy, eV2.4797
Wave speed, m/s299,792,458
Period, s1.668 × 10⁻¹⁵

Speed divided by one of the two

Converts wavelength to frequency and back for light, sound in air and sound in water, and gives the photon energy.

The relationship is simple: wave speed equals wavelength times frequency. Given the speed in a medium, either quantity follows from a division. The difficulty is scale: light is measured in terahertz, radio in megahertz, sound in hertz.

Speed depends on the medium and on the kind of wave. Light in vacuum travels 299,792,458 metres a second, sound in air 343, and in water nearly four and a half times faster. Which is why, underwater, the frequency stays put while the wavelength stretches.

How to use

Choose what to find: frequency, wavelength or speed.
Enter the two you know.
Read the answer together with the period of one oscillation.

Frequency and wavelength trade against each other

Speed is frequency times wavelength, so at a fixed speed one rises as the other falls. For sound at 343 m/s, the note A at 440 Hz has a wavelength of 78 centimetres.

Light travels about a million times faster, and its wavelengths shrink to match: green light at 550 nm corresponds to roughly 545 terahertz. The formula never changes, only the orders of magnitude do.

Worked out with this calculator.
Wave	Speed	Frequency	Wavelength
Sound, note A	343 m/s	440 Hz	0.78 m
FM radio	3 × 10⁸ m/s	100 MHz	3 m
Green light	3 × 10⁸ m/s	545 THz	550 nm

What this calculator shows

Frequency or wavelength from the other one
Frequency in convenient units, from hertz up to terahertz
The colour for visible light and the photon energy in electronvolts

What to keep in mind

Light wavelengths are entered in nanometres and sound wavelengths in metres, as each is conventionally quoted.
Colour boundaries are conventional and the transitions are gradual; the visible range is taken as 380 to 750 nanometres.

FAQs

How are wavelength and frequency related?

Their product is the wave speed in the medium. Shorter wavelength means higher frequency, and the other way round.

How fast is sound in air?

343 metres a second at 20 degrees. It rises by roughly 0.6 metres a second for every degree warmer.

Which wavelength is which colour?

Violet around 400 nm, blue 470, green 530, yellow 580, orange 600, red 650 and above. The boundaries are conventional and the transitions gradual.

How do I calculate photon energy?

Multiply the frequency by Planck's constant. Converted to electronvolts, visible light spans roughly 1.6 to 3.3 eV.

What is the wavelength of a 440 Hz note?

About 78 centimetres, at a sound speed of 343 m/s. Wavelength is simply speed divided by frequency.

Why are radio wavelengths metres and light wavelengths nanometres?

They share a speed but differ in frequency by six orders of magnitude. A hundred megahertz gives three metres; six hundred terahertz gives half a micrometre.

What is the period?

The time for one oscillation, the reciprocal of the frequency. At 440 Hz that is 2.27 milliseconds.

Worked example

Green light

Input: A wavelength of 500 nm in vacuum

Output: 599.585 THz, photon energy 2.48 eV

Note: 500 nm sits in the blue-green part of the visible range. The eye's peak sensitivity in the CIE tables is close by but not here: 555 nm in daylight vision and 507 nm in low light.

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Result

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