How Much Insulation for 500 Square Feet?
Bags or rolls
5 bags
500 square feet of wall or ceiling, framed at 16 inches on center, with 106.8 square foot bags.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Wall or ceiling area500 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls5 bags
| Gross area | 500 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 450 sq ft |
| Bags at 106.8 sq ft | 5 |
| Coverage bought | 534 sq ft |
The material list this produces
| Insulation batts, bags | 5 |
|---|---|
| Vapor retarder, sq ft (if required) | 500 |
Coverage per bag compared
Bag coverage is the number that decides this, and it is printed on the bag. Here is the same area at five common coverages.
| Coverage per bag | Bags or rolls | Coverage bought |
|---|---|---|
| 40 sq ft | 12 bags | 480 sq ft |
| 50 sq ft | 9 bags | 450 sq ft |
| 75 sq ft | 6 bags | 450 sq ft |
| 90 sq ft | 5 bags | 450 sq ft |
| 106.8 sq ft | 5 bags | 534 sq ft |
What else matters here
Five hundred square feet is about the wall area of one good sized room, or the ceiling of a 20 by 25 space. Take the framing off and there are 450 square feet of cavity to fill, which is five bags at the default coverage.
Five bags buys 534 square feet, so there are 84 square feet of batt spare. That is the right amount of spare. Batts get cut short, mis-stapled or wetted, and going back for one more bag costs more in time than the bag costs in money.
Measure the gross area by the outside of the framing and let the calculator take the studs off. Measuring cavity by cavity is slower, gives the same answer, and is how people end up short.
What this calculator assumes
- Framing takes up roughly 10 percent of a wall at 16 inch on center and 7 percent at 24. Cavity area is reduced accordingly, so you do not buy insulation for the studs.
- Bag coverage varies a lot by R value and width. The default is a common R-13 kraft faced batt bag; read your own bag and change it.
Questions people ask
How many bags of insulation for 500 square feet?
Five bags at 106.8 square feet per bag, which covers the 450 square feet of cavity left after framing.
Why is the cavity area less than the wall area?
Because studs and plates take up part of the wall and they are not insulated. Framing runs about 10 percent of a wall at 16 inch on center and about 7 percent at 24 inch, so the calculator takes that off before dividing.
How much does one bag of batts cover?
It is printed on the bag and it moves with R value and width. The default here is a common R-13 kraft faced batt bag at 106.8 square feet. Change it to whatever you are actually buying before you trust the count.
The insulation calculator takes any dimensions you like and hands back the same list.