Find the wavelength, wave speed, or frequency of any wave using the wave equation λ = v / f. Enter any two of the three values and leave the one you want to find blank. Pick a preset wave speed for light or sound, or choose "Custom" to type your own.
The wavelength calculator works with the fundamental wave equation, λ = v / f, which links the three defining properties of any wave: its wavelength (λ), the speed at which it travels (v), and its frequency (f). Enter any two of these quantities and the calculator instantly solves for the third. It comes with a built-in menu of wave speeds — the speed of light in vacuum, air, water, and glass, and the speed of sound in air, water, and various solids — so you can find the wavelength of a radio signal, a beam of light, or a musical note without looking anything up. Each field also has its own unit menu, so you can work in hertz or gigahertz, meters or nanometers, and let the calculator handle the conversions.
Whether you are a physics student checking homework, an engineer designing an antenna, or simply curious how long a wave really is, this tool removes the arithmetic and unit juggling and gives you an exact answer in a single step.
Wavelength is the distance over which a wave's shape repeats — the length of one complete cycle. For a wave drawn as a series of peaks and troughs, it is the distance from one peak to the next (or from any point on the wave to the matching point on the following cycle). Wavelength is measured in units of length: meters for radio waves and sound, and often nanometers for visible light. It is one of the most important properties of a wave because it determines how the wave behaves — how it bends around obstacles, how it interferes with other waves, and, for light, what color we see or what kind of radiation it is.
A long wavelength means the wave's cycles are stretched far apart; a short wavelength means they are packed close together. For a fixed wave speed, wavelength and frequency are inversely related: the higher the frequency, the shorter the wavelength, and vice versa.
The wave equation that this calculator uses is beautifully simple:
λ = v / f
where λ is the wavelength, v is the wave speed (velocity), and f is the frequency. The same relationship can be rearranged to find any of the three quantities:
λ = v ÷ f
v = λ × f
f = v ÷ λ
Frequency is measured in hertz (Hz), where one hertz means one cycle per second. Wave speed is a distance per unit time, usually meters per second (m/s). Divide a speed in meters per second by a frequency in hertz and the seconds cancel, leaving meters — a length, which is exactly what a wavelength should be. The calculator converts whatever units you choose into these base units, computes the result, and then presents it in the unit you selected.
Suppose you want the wavelength of a radio wave with a frequency of 10 MHz traveling at the speed of light. First, the speed of light in vacuum is v = 299,792,458 m/s, and 10 MHz is 10,000,000 Hz. Substituting into the formula:
λ = v ÷ f = 299,792,458 ÷ 10,000,000 = 29.98 m
So the wave is almost 30 meters long. This is the default example loaded into the calculator, so you can press Calculate to see it worked out, then change the numbers or the wave-speed preset to explore other cases. Switch the frequency to 100 MHz and the wavelength drops to about 3 meters; drop it to 1 MHz and the wavelength stretches to nearly 300 meters — a vivid demonstration of the inverse relationship between frequency and wavelength.
A wave's speed is not a fixed number — it depends on what the wave is and what it is traveling through. Light travels fastest in a vacuum, at 299,792,458 m/s, and slows down in denser materials: it moves at about 225 million m/s in water and around 200 million m/s in glass. That slowing is what bends light as it enters a lens or a prism. Sound, by contrast, needs a medium to travel through at all, and it actually moves faster in denser materials: about 343 m/s in room-temperature air, roughly 1,480 m/s in water, and over 6,000 m/s in aluminum. Because wavelength depends on speed, the same frequency produces a different wavelength in each medium. That is why the calculator's preset menu is so useful — choosing the right medium ensures your wavelength is correct. When a wave passes from one medium to another its frequency stays the same, but its speed and therefore its wavelength change.
For light and other electromagnetic waves — all of which travel at the speed of light in vacuum — wavelength is what distinguishes one type of radiation from another. Running from the longest wavelengths to the shortest: radio waves (kilometers down to about a meter), microwaves (centimeters), infrared (micrometers), visible light (about 380 to 700 nanometers), ultraviolet, X-rays, and finally gamma rays (smaller than an atom). Within the visible band, wavelength is what we perceive as color: violet light sits near 400 nm, green around 550 nm, and red near 700 nm. Because the speed is constant for all of these, a higher frequency always means a shorter wavelength, which is why gamma rays are both the highest-frequency and shortest-wavelength form of light.
Sound waves follow the very same equation, but with the speed of sound in place of the speed of light. A musical note at 440 Hz (the standard A above middle C) traveling through 20°C air has a wavelength of 343.2 ÷ 440 ≈ 0.78 meters — about the length of your arm. Bass notes, with their low frequencies, have long wavelengths several meters across, which is why they diffract around corners and are hard to block, while high-pitched sounds have short wavelengths and are more directional. Underwater, where sound travels more than four times faster than in air, the same 440 Hz note has a wavelength of roughly 3.4 meters. The calculator makes it easy to explore how pitch, medium, and wavelength interrelate.
Three quantities describe the timing and spacing of a wave, and they are closely linked. Frequency (f) is how many cycles pass a point each second, measured in hertz. The period (T) is the time for one full cycle, and it is simply the reciprocal of frequency: T = 1 / f. A 10 Hz wave has a period of 0.1 seconds. Wavelength (λ) is the spatial partner of the period — where the period is how long one cycle takes in time, the wavelength is how far the wave travels in that time, which is why λ = v × T = v / f. Keeping these straight makes the wave equation intuitive: multiply how far the wave moves each second (its speed) by how long one cycle lasts (the period), and you get the length of one cycle (the wavelength). Because period and frequency are reciprocals, a wave with a very high frequency has both a tiny period and, for a fixed speed, a tiny wavelength.
To build intuition, here are some familiar waves and their approximate wavelengths, all of which you can reproduce in the calculator:
Notice how electromagnetic waves span an enormous range — from meters for radio down to fractions of a micrometer for light — while audible sound wavelengths run from centimeters to many meters. The single equation λ = v / f covers them all.
The speed of light in a vacuum, exactly 299,792,458 meters per second, is one of the fundamental constants of nature and the fastest speed anything can travel. In any transparent material, light slows down, and the factor by which it slows is called the refractive index (n) of that material. The speed of light in the medium is v = c / n, where c is the vacuum speed. Water has a refractive index of about 1.33, so light travels at roughly 225 million meters per second in it; ordinary glass is around 1.5, slowing light to about 200 million meters per second. Because wavelength depends on speed, light also has a shorter wavelength inside glass or water than in air, even though its frequency — and therefore its color — stays the same. This slowing and the accompanying change in wavelength is the reason lenses focus light and prisms split it into a rainbow. The calculator's light presets already build in these refractive-index adjustments, so choosing "Light in water" or "Light in glass" gives you the correct in-medium wavelength automatically.
Wavelength equals wave speed divided by frequency: λ = v / f. Rearranged, wave speed is v = λ × f and frequency is f = v / λ.
Divide the speed of light (299,792,458 m/s in vacuum) by the light's frequency. For example, a 5 × 10¹⁴ Hz wave has a wavelength of about 600 nm, which is orange light.
The exact speed of light in vacuum, 299,792,458 meters per second. Presets are also included for light in air, water, and glass, where it travels more slowly.
Yes. When a wave enters a new medium its speed changes while its frequency stays the same, so the wavelength changes too. That is why you should select the medium that matches your wave.
Divide the wave speed by the wavelength: f = v / λ. Enter the speed and wavelength in this calculator and leave the frequency field blank to find it.
Any consistent set works because the calculator converts for you. Frequency is commonly in hertz (or kHz, MHz, GHz), speed in meters per second, and wavelength in meters or, for light, nanometers.
This Wavelength Calculator is provided for educational and general informational purposes. It applies the ideal wave equation λ = v / f with standard reference speeds, which vary slightly with temperature, pressure, and material. Verify values independently for critical scientific or engineering work.