Wavelength Converter
Convert wavelength between nanometers, micrometers, millimeters, and meters.
Gives the frequency, the photon energy in eV, and the spectrum band.
Type in any field and the others update instantly.
The panel below gives the frequency, the photon energy, and where it falls on the spectrum.
All conversions use meters (m) as the base unit.
Key conversion factors:
- 1 nanometer (nm) = 0.000000001 m (10⁻⁹ m)
- 1 micrometer (µm) = 0.000001 m (10⁻⁶ m)
- 1 millimeter (mm) = 0.001 m
- 1 centimeter (cm) = 0.01 m
Electromagnetic spectrum reference:
| Type of Radiation | Typical Wavelength |
|---|---|
| Visible light (violet) | ~380 nm |
| Visible light (red) | ~700 nm |
| Near infrared | 0.7 – 2.5 µm |
| Mid infrared | 2.5 – 25 µm |
| Microwave (Wi-Fi 2.4 GHz) | ~125 mm |
| FM radio (100 MHz) | ~3 m |
Wavelength and frequency are inversely related:
λ = c / f where c = speed of light and f = frequency in Hz.
The rough figure for c is 3 × 10⁸ m/s, which is fine for a sanity check. The exact value is 299,792,458 m/s, and it is exact by definition rather than by measurement: since 1983 the metre has been defined as the distance light travels in 1/299,792,458 of a second, so the speed of light is a defined constant and the metre is what follows from it. The converter above uses the exact figure.
Photon energy follows from the frequency:
E = h × f where h is Planck’s constant, 4.1357 × 10⁻¹⁵ eV·s.
That gives the useful shortcut E (eV) ≈ 1240 / λ (nm). Green light at 550 nm carries about 2.25 eV. The 3.1 eV mark, which lands at 400 nm, is roughly where a photon carries enough energy to break a chemical bond, and it is the real dividing line between radiation that warms things and radiation that damages them. Intensity does not change this: a very bright red lamp will never cause sunburn, and a faint ultraviolet one will.
Wavelength is the flip side of frequency, tied together by the speed of the wave, so this converter and a frequency converter really describe the same thing from two angles. High frequency means short wavelength, and the reverse.
Wavelength is what sets physical size in the real world. Antennas are built as fractions of a wavelength, which is why a long-wave radio mast is enormous while a Wi-Fi antenna is tiny. It’s also why bass needs big speakers and big rooms: a low 40 Hz tone has a wavelength of about 8.5 meters, so it interacts with the whole space, while a treble note is only centimeters long. One subtlety the examples above assume is that wave speed depends on the medium. Light slows in glass or water, and sound travels faster in warm air, so the same frequency comes out as a different wavelength depending on what it’s moving through.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.