Light Frequency ↔ Wavelength Converter

c = λν. Convert between wavelength and frequency for any electromagnetic wave.

Inputs

For frequency: Hz, kHz, MHz, THz (use unit selector). For wavelength: m, cm, nm, etc.

Result

Loading calculator…
—

General calculation reads

Amazon affiliate
How Not to Be Wrong
Jordan Ellenberg - math thinking
Shop on Amazon
The Joy of X
Steven Strogatz - accessible math
Shop on Amazon
Scientific calculator (Casio fx-991EX)
Shop on Amazon

As an Amazon Associate we may earn from qualifying purchases. This does not add cost for you.

How to use this calculator

  • Pick which to compute.
  • Enter the value with its unit.
  • Read result with auto-formatted unit and EM band.

About this calculator

For any electromagnetic wave (radio, microwave, IR, visible, UV, X-ray), c = λν where c = 299,792,458 m/s. Visible light is 380-750 nm wavelength, equivalently 400-790 THz frequency. Red light has the longest wavelength (lowest frequency); violet has the shortest.

Frequently asked

Visible-light wavelengths?+
~380 nm (violet) to ~750 nm (red). 600 nm is yellow-orange; 532 nm green; 450 nm blue.
Why does c appear in this formula?+
Because all EM waves travel at c in vacuum. Wavelength × frequency = speed; speed is fixed at c.
Does this work in materials?+
In a medium with refractive index n, light slows to c/n. Frequency stays the same; wavelength shrinks. The calculator assumes vacuum.
Why are different units used for different bands?+
Convenience. Radio: m to mm. Microwave: cm to mm. IR: µm. Visible: nm. X-ray: pm. The calculator auto-picks.
Photon energy from frequency?+
E = hν, where h = 6.626 × 10⁻³⁴ J·s (Planck's constant). 600 THz photon = ~3.97 × 10⁻¹⁹ J = 2.48 eV.

Related calculators

Joule ↔ Electron-Volt Converter
For atomic and particle-physics scales: 1 eV = 1.602176634 × 10⁻¹⁹ J.
Frequency Hz ↔ kHz ↔ MHz ↔ GHz Converter
Bidirectional conversion among Hz / kHz / MHz / GHz / THz.
Lumen to Watt (LED) Calculator
Watts = lumens / efficacy. Modern LEDs hit 100-150 lm/W, vs incandescent ~15 lm/W.
Horsepower to Watts Converter
Convert mechanical (imperial) horsepower to watts. 1 hp = 745.7 W.
kWh to BTU Converter
Convert kilowatt-hours to BTU. 1 kWh = 3,412 BTU.
Electric Field Calculator
Compute electric field from a point charge: E = kQ/r², or from force/charge: E = F/q.

More tools you might like

Hand-picked tools that pair well with this one — same audience, same intent.

Frequency Hz ↔ kHz ↔ MHz ↔ GHz Converter
Calc

Bidirectional conversion among Hz / kHz / MHz / GHz / THz.

Horsepower to Watts Converter
Calc

Convert mechanical (imperial) horsepower to watts. 1 hp = 745.7 W.

kWh to BTU Converter
Calc

Convert kilowatt-hours to BTU. 1 kWh = 3,412 BTU.

Joule ↔ Electron-Volt Converter
Calc

For atomic and particle-physics scales: 1 eV = 1.602176634 × 10⁻¹⁹ J.

Electric Field Calculator
Calc

Compute electric field from a point charge: E = kQ/r², or from force/charge: E = F/q.

Currency Converter
Finance

Convert between 30 major world currencies using a snapshotted static rate table — clearly marked, not live.