Wavelength to Color Calculator
Convert visible light wavelength in nm to color name, hex code, and frequency in THz.
Covers the full spectrum from violet (380 nm) to red (700 nm).
Light wavelength to visible color conversion maps the electromagnetic spectrum’s visible range (approximately 380–780 nanometers) to the colors perceived by the human eye. The relationship between wavelength and color is determined by physics, but the subjective experience of color also involves the eye’s cone cells.
Speed of light formula (connecting wavelength and frequency): c = λ × f
Therefore: Frequency (f) = c ÷ λ Wavelength (λ) = c ÷ f
Where:
- c = speed of light = 299,792,458 m/s (≈ 3 × 10⁸ m/s)
- λ (lambda) = wavelength in meters (or nanometers: 1 nm = 10⁻⁹ m)
- f = frequency in hertz (Hz)
Energy of a photon: E = h × f = h × c ÷ λ
Where:
- h = Planck’s constant = 6.626 × 10⁻³⁴ J·s
- Higher frequency (shorter wavelength) = more energetic photons
The visible spectrum (approximate wavelength ranges): These are the exact boundaries the calculator above uses, so the two always agree. Published tables differ by 10 to 20 nm at each edge, because the colour bands blend rather than switch, and no two references draw the lines in the same place.
| Color | Wavelength (nm) | Frequency (THz) |
|---|---|---|
| Violet | 380–450 | 666–789 |
| Blue | 450–485 | 618–666 |
| Cyan | 485–500 | 600–618 |
| Green | 500–565 | 531–600 |
| Yellow | 565–590 | 508–531 |
| Orange | 590–625 | 480–508 |
| Red | 625–700 | 428–480 |
Deep red continues past 700 nm to roughly 780 nm before it fades into infrared, but the sRGB approximation used here stops being meaningful up there, so the calculator tops out at 700.
What each variable means:
- Nanometer (nm): one billionth of a meter; the standard unit for visible light wavelengths
- Terahertz (THz): the frequency unit; 1 THz = 10¹² Hz; visible light oscillates hundreds of trillions of times per second
- Beyond visible: UV light < 380nm (causes sunburn); infrared > 780nm (felt as heat)
- Perceived color vs. physical wavelength: color perception also depends on context, surrounding colors, and individual variation in cone cell sensitivity
Worked example: Laser pointer wavelength: 532 nm (common green laser).
- Frequency = c ÷ λ = 299,792,458 ÷ (532 × 10⁻⁹) = 5.635 × 10¹⁴ Hz = 563.5 THz
- Color: Green (500–565 nm range): confirmed ✓
- Energy per photon = h × f = (6.626 × 10⁻³⁴) × (5.635 × 10¹⁴) = 3.734 × 10⁻¹⁹ joules per photon (2.33 eV)
Round c off to 3 × 10⁸ and the same sum gives 563.9 THz. The calculator uses the exact speed of light, so it reads 563.5, and that is the figure to trust.
The human eye is most sensitive to green light (~555 nm), which is why night vision equipment uses green displays and many safety signals use green color.
How we build and check this calculator
This calculator 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.
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