Insulation Calculator
Enter your wall area and the coverage per pack to get the number of insulation batts or rolls you need.
What your result means
This is how many batt packs or rolls cover your wall area at your product's coverage per pack. Add 5 to 10% for waste. Match the R-value to the cavity and climate (R-13 for 2x4 walls, R-19 for 2x6), face the vapor barrier toward the warm side, and wear PPE since fiberglass irritates skin and lungs.
How to use this calculator
- Calculate total wall sq ft.
- Check insulation packaging for coverage per pack.
- Read packs/rolls needed.
- Add 5-10% for waste.
- Choose R-value appropriate for your climate.
The formula
Divide the wall area by the coverage per pack and round up for the number of packs.
Worked example
Say you've got 800 sq ft of wall and each pack covers 75 sq ft. That's 11 packs.
Insulation R-value guide
| Location | R-value |
|---|---|
| 2x4 wall | R-13 |
| 2x6 wall | R-19 |
| Ceiling / attic (cold) | R-30+ |
Tips & gotchas
- R-13 for 2x4 walls is standard.
- R-19 for 2x6 walls insulates better.
- R-30 for ceilings and attics in cold climates.
- Faced insulation has a vapor barrier; face it toward the warm side.
- Wear PPE; fiberglass irritates skin and lungs.
Frequently asked questions
How much insulation do I need?
Find your wall square footage and divide by the coverage per pack, usually 75 sq ft.
What R-value should I use?
R-13 for 2x4 walls, R-19 for 2x6, higher for ceilings.
Fiberglass batt or spray foam?
Batt is cheapest; spray foam performs best but costs more.
Should I get faced insulation?
Yes for walls. Face the vapor barrier toward the warm side.
How long does fiberglass insulation last?
50-plus years if it stays dry.
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Estimates only — see our full disclaimer.