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Wavelength & Frequency Calculator

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Guide

Wavelength & Frequency Calculator

Convert between wavelength (λ) and frequency (f) for any electromagnetic wave — radio, microwave, infrared, visible light, ultraviolet, X-ray, or gamma. Enter either value, choose a unit, and instantly see the corresponding frequency or wavelength, the photon energy in eV and joules, and the position of your value on a log-scaled spectrum bar. For visible wavelengths, the tool also renders an approximate perceived color so you can see what 550 nm or 450 nm looks like.

How to Use

Pick an Input Mode — “Wavelength → Frequency” or “Frequency → Wavelength”.
Type the value and select the unit (nm/µm/mm/cm/m for wavelength; Hz/kHz/MHz/GHz/THz for frequency).
Or pick a Common Source preset — FM radio, Wi-Fi, microwave oven, visible red/green/blue, UV-A, or X-ray — to fill the inputs in one click.
Read the spectrum bar marker, the band tag (Radio/Microwave/IR/Visible/UV/X-Ray/Gamma), and the photon energy in the result table.

Features

Bidirectional conversion — input either λ or f and the other is computed using λ = c / f with c = 299,792,458 m/s.
Multi-unit input and output — wavelength in nm, µm, mm, cm, m; frequency in Hz, kHz, MHz, GHz, THz.
Log-scale spectrum bar with a marker showing exactly where your value falls across 18 decades of the EM spectrum.
Photon energy reported in electron-volts (eV) and joules (J) using E = h·f with h = 6.62607015 × 10⁻³⁴ J·s.
Visible-light color preview — for wavelengths between 380 and 780 nm, an RGB swatch approximates the perceived color.
Common source presets for FM broadcast, Wi-Fi 2.4/5 GHz, microwave ovens, red/green/blue light, UV-A, and X-ray.
Auto-updating — results refresh as you type; no submit button needed.

Common Use Cases

RF and antenna engineering — checking quarter-wave or half-wave antenna lengths.
Optics and photonics — picking laser wavelengths and verifying photon energies.
Physics and chemistry homework — converting between wavelength, frequency, and photon energy.
Photography and color science — looking up the wavelength of a specific color or LED emission.
Spectroscopy — confirming whether a measured peak falls in IR, visible, or UV bands.

 FAQ

What is the relationship between wavelength and frequency?

Wavelength (λ) and frequency (f) of an electromagnetic wave are inversely proportional and connected by the speed of light: λ × f = c, where c ≈ 299,792,458 m/s in a vacuum. Doubling the frequency halves the wavelength, and vice versa. This relationship holds for radio waves, light, X-rays, and every other EM wave.
How is photon energy calculated from frequency or wavelength?

Photon energy is given by E = h·f, where h is Planck's constant (6.62607015 × 10⁻³⁴ J·s). Because λ·f = c, you can also write it as E = h·c / λ. Energy is most often expressed in electron-volts (1 eV = 1.602176634 × 10⁻¹⁹ J), with visible photons sitting around 1.6–3.3 eV and X-ray photons in the keV range.
Why do colors look different at different wavelengths?

The human eye contains three types of cone cells sensitive to long (~564 nm), medium (~534 nm), and short (~420 nm) wavelengths. The brain interprets the relative response of these cones as color. Around 700 nm we perceive red, around 550 nm green, and around 450 nm blue. Outside roughly 380–780 nm we see nothing at all — those wavelengths are infrared or ultraviolet.
What divides ionizing from non-ionizing radiation?

Photons with enough energy to remove tightly bound electrons from atoms or molecules are called ionizing. The conventional threshold is about 10 eV, which corresponds to a wavelength near 124 nm in the far ultraviolet. UV-C, X-rays, and gamma rays are ionizing; visible light, infrared, microwaves, and radio waves are not.