๐งฑ Construction
R-Value Calculator
R-value measures resistance to heat flow, and R equals thickness divided by thermal conductivity. Layers add up, but the air films on the inside and outside of a wall also contribute, so a measured cavity rarely matches the nominal figure.
How it works
Material thickness
Thermal conductivity (k)
Number of identical layers
Include surface air films
R-value (imperial)
R-value (metric)
U-factor
Total thickness
Frequently asked questions
How do I use the R-Value Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.