Insulation R-Value Calculator

About this calculator

This calculator finds the R-value of an insulation material — its resistance to heat flow — from the material's thickness and its R-value per inch (or per unit thickness), since R-value scales linearly: total R = thickness × R-per-inch. A higher R-value means better insulating performance.

Homeowners and contractors use it to compare insulation options (fiberglass batts, spray foam, rigid foam board) and to check whether a wall, attic, or floor assembly meets local building-code minimums. Energy auditors also use R-value totals when estimating a building's heat loss.