Wavelength-Frequency Converter

Convert between wavelength and frequency instantly. Calculate the wavelength, frequency, and energy of light, sound, and radio waves. Free online wavelength-frequency converter.

How to Use

  1. Choose conversion direction

    Select whether to convert wavelength to frequency or frequency to wavelength.

  2. Enter value

    Input the wavelength or frequency value and select the unit.

  3. View results

    Click Calculate to see the converted value and energy (eV).

What are wavelength and frequency?

Wavelength (λ) is the distance a wave travels during one complete oscillation — the gap from one crest to the next, measured in meters (m). Frequency (f) is the number of oscillations that occur in one second, expressed in hertz (Hz).

When a wave travels at a constant speed, the two quantities are inversely proportional. In other words, as the wavelength gets shorter, more crests pass by in the same amount of time, so the frequency rises. This converter lets you pick light (electromagnetic waves) or sound (acoustic waves) and calculate one value from the other, along with the period and the spectrum band, all at once.

This relationship is widely used to find the wavelength of a radio broadcast channel from its frequency, to determine which color or region a light wavelength measured by a spectrometer belongs to, and to design antenna lengths.

Formula

The wave speed c equals the product of frequency and wavelength.

c = f × λ → f = c / λ, λ = c / f, T = 1 / f

Example — finding the frequency of a wavelength λ = 550 nm (550×10⁻⁹ m) using the speed of light c = 299,792,458 m/s: f = 299792458 / (550×10⁻⁹) ≈ 5.45×10¹⁴ Hz, with a period of T = 1/f ≈ 1.83×10⁻¹⁵ s, which falls in the visible (green) region.

Here c is the wave speed, f is the frequency (Hz), λ is the wavelength (m), and T is the period of one oscillation (s).

Frequently Asked Questions

What is the relationship between wavelength and frequency?
Wavelength (λ) and frequency (f) are inversely proportional. When the wave speed (c) is constant, c = f × λ, so a longer wavelength means a lower frequency and a shorter wavelength means a higher frequency. Electromagnetic waves use the speed of light (about 3×10⁸ m/s), while sound waves use the speed of sound (about 343 m/s).
Which speed values does this calculator use?
For electromagnetic waves (light) it uses the exact speed of light in a vacuum, c = 299,792,458 m/s. For sound waves it uses 343 m/s, the speed of sound in air at 20°C. In other media such as water or metal the speed of sound differs, so the results change accordingly.
What is the electromagnetic spectrum?
It is the classification of electromagnetic waves by wavelength. From shortest to longest wavelength, it ranges through gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. For electromagnetic results, this calculator automatically displays the spectrum band the wavelength falls into.
What is the wavelength range of visible light?
Visible light that the human eye can see spans roughly 400 nm (violet) to 700 nm (red). Shorter than this is ultraviolet (UV) and longer is infrared (IR), neither of which is visible to the naked eye.
What units are used for wavelength?
Wavelength uses the meter (m) as its base unit, but is also expressed in nanometers (nm, 10⁻⁹ m), micrometers (μm, 10⁻⁶ m), and millimeters (mm). Light is usually given in nm, radio waves in m, and microwaves in cm to mm.
What is the period (T) and how do you find it?
The period is the time it takes a wave to complete one full oscillation, measured in seconds (s). It is the reciprocal of frequency, so T = 1 / f. For example, a frequency of 100 Hz gives a period of 0.01 seconds.
What is the audible frequency range?
The frequency of sound a human can hear is roughly 20 Hz to 20,000 Hz (20 kHz). Below 20 Hz is infrasound and above 20 kHz is ultrasound. As people age, high-frequency hearing declines and the upper audible limit drops.
Can finding the wavelength from a radio frequency help with antenna design?
Yes. For example, the wavelength of a 100 MHz FM signal is c / f = 299,792,458 / 10⁸ ≈ 3 m. Antennas are usually designed at 1/2 or 1/4 of the wavelength, so finding the wavelength first with this converter helps you estimate a suitable antenna length.
2026 physical constants

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