Heat flux calculator

These equivalent expressions give heat flow per unit area; multiply by area for total heat rate.

Units

q = \frac{\Delta T}{R_{\text{total}}}

Calculator

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

Given

q = \frac{72}{16} = 4.5

Symbol	Meaning	Unit
$q$	heat flux, not total-area heat rate	Btu/(h·ft²)
$\Delta T$	temperature difference	°F
$R_{\text{total}}$	total resistance	h·ft²·°F/Btu

Symbol	Meaning	Unit
$q$	heat flux, not total-area heat rate	W/m²
$\Delta T$	temperature difference	K
$R_{\text{total}}$	total resistance	m²·K/W

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