Enter a wave speed and frequency to calculate the corresponding wavelength using the formula λ = v / f. Choose from common wave speed presets (light in vacuum, sound in air, etc.) or enter a custom speed, then select your preferred units for each value. You get back the wavelength along with a breakdown of all three wave properties.
Wavelength (λ)
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Wave Speed (v)
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Frequency (f)
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Wave Period (T)
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Wavenumber (k)
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The wavelength formula is λ = v / f, where λ is the wavelength in meters, v is the wave speed in meters per second, and f is the frequency in Hertz. You can rearrange this to find speed (v = λ × f) or frequency (f = v / λ) if you know the other two variables.
Frequency and wavelength are inversely proportional — as frequency increases, wavelength decreases, and vice versa, assuming the wave speed remains constant. This is why high-frequency radio waves (like GHz signals) have very short wavelengths, while low-frequency sound waves have long wavelengths.
Wavelength is measured in meters (m) in the SI system. However, depending on the application, other units are common: nanometers (nm) for visible light, centimeters or millimeters for microwave signals, and meters for radio waves and sound. This calculator lets you choose your preferred output unit.
The speed of light in a vacuum is exactly 299,792,458 m/s (approximately 3 × 10⁸ m/s). Light travels slightly slower through other media — about 299,700,000 m/s in air, 224,901,000 m/s in water, and around 197,000,000 m/s in glass, depending on the refractive index.
The wavenumber k (in rad/m) is related to wavelength by the formula k = 2π / λ. So to get wavelength from wavenumber, use λ = 2π / k. This calculator displays the wavenumber as a secondary result once you've entered the frequency and wave speed.
The energy of a photon is calculated using E = hf = hc / λ, where h is Planck's constant (6.626 × 10⁻³⁴ J·s), c is the speed of light, and λ is the wavelength. Shorter wavelengths correspond to higher energy — this is why UV and X-ray radiation carry more energy than visible light or infrared.
Red light has the longest wavelength in the visible spectrum, ranging from approximately 620 to 750 nm. Violet light has the shortest visible wavelength (around 380–450 nm). Infrared radiation has even longer wavelengths than red light but is not visible to the human eye.
When a wave passes from one medium to another, its frequency stays constant but its speed changes, which means its wavelength also changes. For example, light slows down and its wavelength shortens when entering water or glass. This change in wavelength (and speed) is what causes refraction — the bending of waves at a boundary.