How do I calculate wavelength?

Divide wave speed by frequency. For electromagnetic waves in air, the speed is usually approximated as the speed of light.

What is the wavelength of 100 MHz?

Using the speed of light, 100 MHz has a wavelength of about 3 meters.

Does frequency change when light enters glass?

Frequency is set by the source. Speed and local wavelength change when the wave enters a different medium.

Wavelength Calculator

Calculate wavelength, frequency, wave speed, period and wave number for light, radio waves, sound and custom media.

Wavelength calculator

Wave type / medium

Wave speed: 299,792,458 m/s

For radio waves and light in air, the vacuum speed of light is usually a practical approximation.

Known value

Frequency

Wavelength from frequency and speed

English search intent expects the basic wave relationship, with quick presets for electromagnetic waves, sound in air and custom wave speed.

λ = \frac{v}{f}

lambda is wavelength, v wave speed and f frequency.

T = \frac{1}{f}

T is the period of one cycle.

k = \frac{2 π}{λ}

k is angular wave number.

Medium and spectrum limits

Speed depends on the medium

Light in glass, sound in air and sound in water use different propagation speeds. For precise acoustics, optics or RF design, use measured medium data and engineering references.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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