Convert a peak wavelength in nm to temperature in kelvin with Wien’s law, or find the peak wavelength from a temperature in K, °C or °F.

Wien’s law gives a blackbody’s peak wavelength. A single laser or emission-line wavelength does not set a temperature.

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nm to Temperature Formula

The following formula estimates blackbody temperature from its peak wavelength in a spectrum expressed per unit wavelength. An arbitrary emitted wavelength alone does not determine source temperature.

T = (b) / (λ)

Variables:

  • T is the temperature in kelvin
  • b is Wien's displacement constant (approximately 2.898 x 106 nm·K)
  • λ is the blackbody peak wavelength in nanometers (spectral radiance per unit wavelength)

To calculate the temperature, divide Wien's displacement constant by the wavelength.

Nanometers to Temperature Conversion Table (Wien's law, b = 2.898×10^6 nm·K)
Wavelength (nm) Temperature (K) Temperature (°C) Temperature (°F)
10028980.028706.951704.3
20014490.014216.925622.3
3009660.09386.916928.3
3807626.37353.213267.7
4007245.06971.912581.3
4506440.06166.911132.3
5005796.05522.99973.1
5505269.14995.99024.7
6004830.04556.98234.3
6504458.54185.37565.6
7004140.03866.96992.3
8003622.53349.46060.8
9003220.02946.95336.3
10002898.02624.94756.7
15001932.01658.93017.9
20001449.01175.92148.5
3000966.0692.91279.1
4000724.5451.4844.4
5000579.6306.5583.6
10000289.816.762.0
Using Wien's displacement law: T(K) ≈ 2.898×10^6 nm·K ÷ λ(nm). Values rounded to 1 decimal place.

What is the Relationship Between Wavelength and Temperature?

The relationship between wavelength and temperature is described by Wien's displacement law. This law states that the wavelength at which the emission of a black body spectrum is maximized is inversely proportional to the temperature of the black body. In simpler terms, as the temperature of an object increases, the peak wavelength of its emitted radiation shifts to shorter wavelengths. This principle is fundamental in fields such as astrophysics and thermal imaging, where it helps in determining the temperature of stars and other celestial bodies based on their emitted light.

How to Calculate Temperature from Wavelength?

The following steps outline how to calculate the temperature from the wavelength.

  1. First, determine the wavelength (λ) in nanometers.
  2. Next, use Wien's displacement constant (b), which is approximately 2.898 x 106 nm·K.
  3. Calculate the temperature (T) using the formula T = b / λ.
  4. Finally, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Wavelength (λ) = 500 nm

Wien's displacement constant (b) = 2.898 x 106 nm·K