R-Value Insulation Calculator (Total from Layers)
Enter the R-value of each insulation layer (leave unused layers at 0) to calculate the total combined R-value.
R-Value Insulation Calculator (Total from Layers)
Calculate the total R-value of a wall, roof or floor assembly by adding up the R-values of each insulation layer.
This calculator provides a material estimate for general planning purposes only. Always add a safety margin and confirm quantities with your supplier or contractor before purchasing, since real-world waste, layout and offcuts vary by project.
R-value measures resistance to heat flow, and for layers in series (like insulation, sheathing and drywall in a wall), the total R-value is simply the sum of each layer's individual R-value.
Example
- With the default values shown above, this calculator returns: Total R-Value ≈ 18.00.
Frequently Asked Questions
How do R-values combine?
R-values for layers stacked in the same direction of heat flow simply add together, so the total insulating power of an assembly is the sum of every layer's R-value.
What if I only have 2 layers?
Leave the unused layer fields at 0 — they won't affect the total.