Radiant Heat Calculator


Calculating radiant heat output is crucial for designing efficient heating systems in various applications, such as buildings and industrial processes. With the right formula and tools, you can accurately determine the amount of radiant heat emitted by a surface. This article presents a simple calculator to help you perform these calculations effortlessly.

How to Use

To use the radiant heat calculator, follow these steps:

  1. Enter the surface temperature in Celsius (°C).
  2. Enter the emissivity value of the material.
  3. Click the “Calculate” button to obtain the radiant heat output in watts per square meter (W/m²).


The formula used in this calculator is the Stefan-Boltzmann Law:


  • Q is the radiant heat output (W/m²)
  • ϵ is the emissivity of the material (unitless, typically between 0 and 1)
  • σ is the Stefan-Boltzmann constant (5.67×10−8 W/m2K45.67×10−8W/m2K4)
  • T is the temperature of the surface in Kelvin (K)

Example Solve

Let’s say we have a surface with a temperature of 100°C and an emissivity of 0.9. Plugging these values into the formula:


Q: What is emissivity?

Emissivity is the measure of an object’s ability to emit infrared energy. It ranges from 0 to 1, with higher values indicating better emission.

Q: Can I use this calculator for different units of temperature?

Yes, you can use any unit of temperature as long as you convert it to Celsius before entering it into the calculator.

Q: Is this calculator suitable for all materials?

Yes, as long as you provide the correct emissivity value for the material, you can use this calculator for various surfaces.


Calculating radiant heat output is essential for designing efficient heating systems. With the radiant heat calculator and the Stefan-Boltzmann Law, you can accurately determine the amount of heat emitted by a surface, aiding in the optimization of heating processes and energy usage.

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