Equivalent pipe-insulation thickness calculator

Use the natural logarithm and consistent radii; nominal pipe size does not equal outside diameter.

Units

d' = r_{2} \times \ln\left(\frac{r_{2}}{r_{1}}\right)

Calculator

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

Given

d' = 4.1 \times \ln\left(\frac{4.1}{2.1}\right) \approx 2.743

Symbol	Meaning	Unit
$d'$	equivalent thickness referred to outside insulation area	in
$r_{1}$	outside radius of bare pipe	in
$r_{2}$	outside radius including insulation	in

Symbol	Meaning	Unit
$d'$	equivalent thickness referred to outside insulation area	m
$r_{1}$	outside radius of bare pipe	m
$r_{2}$	outside radius including insulation	m

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