What R-value do I need for my climate?

Required R-values are set by building codes and vary by climate zone, colder regions require higher R-values (often R-38 to R-60 in attics), while milder climates can use less. Check your local energy code or a national climate zone map for the correct target.

Why does required thickness change with the material I select?

Different insulation materials have different R-value per inch (their thermal resistance density), spray foam is denser than fiberglass batt for example, so it reaches the same target R-value in a thinner layer.

Insulation Calculator

Find the required insulation thickness and volume for a target R-value.

How this is calculated

Thickness = Target R-value ÷ Material's R-value per inch

Assumptions used in this calculation

Ideal installation: Uses the material's nominal, lab-tested R-value per inch, real-world performance drops with compression, gaps, or improper installation.
No vapor barrier or air sealing accounted: Calculates insulation thickness only, it doesn't factor in the added performance of air sealing or vapor barriers, which also affect real-world energy efficiency.

About this calculator

The insulation calculator finds the thickness and volume of insulation material needed to reach a target R-value over a given area, for common insulation materials.

Worked example

500 sqft, R-30, fiberglass batt

Result: 8.57 in thick

Was this helpful?

Frequently asked questions

HVAC / BTU Calculator

Calculate the AC/HVAC size needed for a room based on area and climate.

Insulation Calculator

About this calculator

Frequently asked questions

What R-value do I need for my climate?

Why does required thickness change with the material I select?

Related calculators