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Calculation Machine

Insulation Calculator

Batts or rolls needed by R-value.

Reviewed by the Calculation Machine team · How we check our maths

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.

Worked example

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

Result

  • Bags or rolls needed20
  • Area with 5% waste945 sq ft
  • Target R-valueR-38
  • Estimated cost$840.00
  • Cost per square foot$0.93

How to use the Insulation Calculator

  1. 1Measure the area to be insulated.
  2. 2Check coverage per bag on the label.
  3. 3Pick the R-value recommended for your climate zone.

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