What is Wien's displacement law?

Wien's displacement law states that the peak wavelength of a blackbody's emission spectrum is inversely proportional to its absolute temperature: λ_max = b / T. The constant b = 2.897771955 × 10⁻³ m·K.

Why does the Sun's peak wavelength fall in the green range?

The Sun's surface temperature is roughly 5778 K, giving a peak wavelength of about 501 nm, which is in the green part of the visible spectrum. However, the Sun emits across all visible wavelengths, so it appears white or yellow-white.

What temperature is required for visible light emission?

To peak in the visible range (400–700 nm), a blackbody must be between about 4140 K (red end) and 7250 K (violet end). Objects below ~1000 K emit mostly in the infrared.

Does this apply to real objects or only ideal blackbodies?

Wien's law applies exactly to ideal blackbodies. Real objects have an emissivity less than 1, which shifts and flattens the spectrum, but the peak wavelength estimated here is a close approximation for many practical materials.

What is the minimum temperature this calculator supports?

Temperatures must be above absolute zero (0 K / −273.15 °C / −459.67 °F). The calculator enforces this limit and shows an error for non-physical inputs.

Blackbody Peak Wavelength Calculator

Enter a temperature and get the peak emission wavelength of a blackbody using Wien's displacement law (λ_max = b / T).

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Summary

A blackbody is a theoretical object that absorbs all radiation and emits light purely based on its temperature. Wien's displacement law states that the peak emission wavelength is inversely proportional to temperature: λ_max = b / T, where b is Wien's displacement constant (2.897771955 × 10⁻³ m·K). This calculator converts any temperature to the corresponding peak wavelength and identifies which part of the electromagnetic spectrum it falls in.

How it works

Enter the temperature of the blackbody in Kelvin, Celsius, or Fahrenheit.
The calculator converts your input to Kelvin if needed.
Wien's displacement law (λ_max = b / T) is applied, where b = 2.897771955 × 10⁻³ m·K.
The resulting peak wavelength is displayed in nanometers (nm) and micrometers (µm).
The spectral region (gamma ray through radio wave) is identified based on the wavelength.
A visual color bar shows where the peak falls in the visible spectrum if applicable.

Use cases

Determine at what wavelength the Sun emits most of its light (~500 nm, visible green).
Find the peak infrared wavelength emitted by a human body (~9.5 µm at 37 °C).
Calculate peak emission for incandescent bulb filaments (~1000 nm near-infrared).
Estimate peak wavelength for stars based on their surface temperature.
Check what wavelength industrial furnaces peak at for thermal imaging.
Verify astrophysics and thermodynamics homework problems.

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Last updated: 2026-06-15 · Reviewed by Nham Vu