Home & DIY Calculators
Insulation R-Value Calculator
Add each insulation layer's material and thickness to calculate your total combined R-value.
R-19.2
Total R-19.2
R-values add directly when layers are stacked in series. The per-inch values above are commonly cited approximations — always check your specific product's printed R-value, since real-world performance varies by manufacturer and installation quality.
How to use this tool
- 1Choose a material preset or enter a custom R-value per inch.
- 2Enter that layer's thickness.
- 3Add more layers as needed.
- 4See your total R-value.
Frequently asked questions
Do R-values just add up?+
Yes — R-values add directly in series when layers are stacked, which is why combining batt insulation with rigid foam board increases total R-value.