Insulation Calculator
Batts or rolls needed by R-value.
Enter your values
ⓘ Live results
Results
- Bags or rolls needed
- 20
- Area with 5% waste
- 945 sq ft
- Target R-value
- R-38
- Estimated cost
- $840.00
- Cost per square foot
- $0.93
Quick answer
Insulation is sized by area and R-value; higher R means more thickness and better heat resistance.
How to use the Insulation Calculator
- 1Measure the area to be insulated.
- 2Check coverage per bag on the label.
- 3Pick the R-value recommended for your climate zone.
Worked example
Using the values the calculator loads with:
Inputs
- Area to insulate900 sq ft
- Coverage per bag/roll48 sq ft
- Price per bag/roll42 $
- Target R-valueR-38 attic
Results
- Bags or rolls needed20
- Area with 5% waste945 sq ft
- Target R-valueR-38
- Estimated cost$840.00
- Cost per square foot$0.93
Frequently asked questions
What R-value do attics need?
R-38 to R-60 depending on climate zone.
Can I add over old insulation?
Yes, as long as the new layer is unfaced.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.