Wavelength to Color Calculator
The visible spectrum spans from approximately 380 nm (violet) to 750 nm (deep red). Each wavelength corresponds to a perceived color and a specific photon energy. The energy-wavelength relationship is E = hc/lambda, where h is Planck's constant (6.626e-34 J s) and c is the speed of light (2.998e8 m/s). In practical units, E (eV) = 1240 / lambda (nm). Frequency is given by f = c/lambda. This calculator maps a wavelength to its approximate color region, photon energy in electron volts, frequency in terahertz, and wavenumber (reciprocal of wavelength in cm) used in spectroscopy.
Wavelength to energy and frequency formulas
E (eV) = 1240 / lambda (nm)
f (Hz) = c / lambda = 2.998e8 m/s / lambda (m)
Wavenumber (cm-1) = 1e7 / lambda (nm)
Where c = 2.99792458e8 m/s (speed of light in vacuum) per NIST CODATA. h = 6.62607e-34 J s (Planck's constant). 1 eV = 1.602e-19 J.
Visible spectrum color regions
- Violet: 380 to 450 nm (3.1 to 2.76 eV)
- Blue: 450 to 495 nm (2.76 to 2.50 eV)
- Cyan: 495 to 520 nm (2.50 to 2.38 eV)
- Green: 520 to 565 nm (2.38 to 2.19 eV)
- Yellow: 565 to 590 nm (2.19 to 2.10 eV)
- Orange: 590 to 625 nm (2.10 to 1.98 eV)
- Red: 625 to 750 nm (1.98 to 1.65 eV)
Wavelength and color: frequently asked questions
What is the visible spectrum?
The visible spectrum of light ranges from approximately 380 nm (violet) to 750 nm (deep red). The color regions are: violet 380-450 nm, blue 450-495 nm, cyan 495-520 nm, green 520-565 nm, yellow 565-590 nm, orange 590-625 nm, red 625-750 nm. These boundaries are approximate as color perception is continuous and varies between individuals.
What is the photon energy at a given wavelength?
Photon energy E = hf = hc/lambda, where h = 6.626e-34 J s (Planck's constant), c = 2.998e8 m/s, and lambda is the wavelength in meters. In electron volts (eV): E = 1240 / lambda(nm). So 550 nm green light has photon energy of 1240/550 = approximately 2.25 eV.
How is wavelength related to frequency?
The relationship is c = f x lambda, where c is the speed of light (2.998e8 m/s in vacuum), f is frequency in Hz, and lambda is wavelength in meters. At 550 nm, frequency = 2.998e8 / 550e-9 = 5.45e14 Hz = 545 THz.
Why do we see certain colors as more intense?
Human photopic (daylight) vision is most sensitive near 555 nm (yellow-green), which is close to the peak of the Sun's visible output. The CIE 1931 luminosity function V(lambda) describes this sensitivity curve. Sensitivity drops off toward both red and violet ends.
What is beyond the visible spectrum?
Ultraviolet (UV) light is below 380 nm (higher energy, shorter wavelength). Infrared (IR) is above 750 nm (lower energy, longer wavelength). Near-IR extends from 750 nm to about 1400 nm. X-rays are below about 10 nm. The entire electromagnetic spectrum follows the same c = f x lambda relationship.
Official sources
- NIST CODATA, Fundamental Physical Constants (c, h). physics.nist.gov.
- OpenStax University Physics Volume 3, Chapter 1: The Nature of Light. openstax.org.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.