Thermal Resistance Converter

Convert R-values and other thermal resistance units, the figures used to rate insulation performance in construction.

What an R-Value Actually Measures

Thermal resistance, most commonly encountered as the R-value printed on insulation packaging, measures how effectively a material resists the flow of heat through it, meaning a higher R-value represents better insulating performance, since the material more effectively slows heat trying to pass through from a warmer side to a cooler side. R-value is specifically defined as the inverse of thermal conductivity multiplied by the material’s thickness, which is exactly why insulation performance depends on both what the material is made from and how thick a layer of it is installed, meaning doubling the thickness of a given insulation material genuinely doubles its R-value, a straightforward and useful relationship when comparing different insulation thicknesses of the same material. Comparing R-values between the US customary system and the metric system, which uses a related but differently scaled measure, requires converting the underlying heat flow, area, and temperature units the R-value is built from, which is exactly why an insulation product’s R-value rating can look numerically very different between a US specification sheet and a European one describing genuinely identical thermal performance, purely because of which unit system the underlying figure was calculated in.