Radiation-loss estimate calculator

The stated radiation estimate assumes unit emissivity and uses absolute temperatures to the fourth power.

Units

q_{\text{rad}} = A \times 0.1714 \times 10^{-8} \times \left(T_{\text{s,R}}^{4} - T_{\text{room,R}}^{4}\right)

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

q_{\text{rad}} = 100 \times 0.1714 \times 10^{-8} \times \left({760}^{4} - {530}^{4}\right) \approx 43{,}658

Symbol	Meaning	Unit
$q_{\text{rad}}$	radiative heat loss	Btu/h
$T_{\text{room,R}}$	ambient absolute temperature	°R
$T_{\text{s,R}}$	surface absolute temperature	°R
$A$	surface area	ft²

Symbol	Meaning	Unit
$q_{\text{rad}}$	radiative heat loss	kW
$T_{\text{room,K}}$	ambient absolute temperature	K
$T_{\text{s,K}}$	surface absolute temperature	K
$A$	surface area	m²

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.