Insulation Calculator

Find the depth of insulation needed to bring an attic or wall up to a target R-value, by insulation type.

ft²
Attics in most U.S. climate zones: R-49 to R-60 (IECC 2021).

Additional depth needed

15.2 in

  • R-value to add38
  • Volume of insulation1,267 ft³
  • Area1,000 ft²

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Enter the area.
  2. Pick the insulation type.
  3. Enter the existing and target R-values.

The formula

Depth to add = (target R − existing R) ÷ R-value per inch

Worked example

Area to insulate1000 ft²
Insulation typeBlown fiberglass (≈R-2.5 per in)
Existing R-value11
Target R-value49

Result

Additional depth needed15.2 in
R-value to add38
Volume of insulation1,267 ft³
Area1,000 ft²

Tips before you order

  • Air-seal the attic floor before adding insulation — gaps cut performance more than thin spots.
  • Product bags list the exact coverage and settled depth for each R-value; use those for buying.

Questions

How much attic insulation do I need?

In most U.S. climate zones, current energy codes call for R-49 to R-60 in attics.