Thermal Radiation Calculator

Calculate net radiative heat transfer using the Stefan–Boltzmann law. Solve for heat transfer rate, emissivity, surface area or absolute temperature.

1. Choose what to calculate

What do you want to calculate?

2. Enter known values

Material and geometry

A value from 0 to 1 describing how effectively the surface emits radiation; 1 is an ideal black body.

Temperatures

Radiation calculations convert the selected input units to absolute temperatures in Kelvin.

Heat transfer

The Stefan–Boltzmann constant is fixed: σ = 5.67 × 10⁻⁸ W/(m²·K⁴).

Q is a heat-transfer magnitude. When solving a temperature, this model assumes the object is at least as warm as its surroundings.

Resets fields and units to their defaults. Saved calculations remain.

Save calculation

Saves the inputs, selected units, and current calculated result.