How Much Insulation for 1200 Square Feet?
Bags or rolls
11 bags
1,200 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 area1200 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls11 bags
| Gross area | 1,200 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 1,080 sq ft |
| Bags at 106.8 sq ft | 11 |
| Coverage bought | 1,175 sq ft |
The material list this produces
| Insulation batts, bags | 11 |
|---|---|
| Vapor retarder, sq ft (if required) | 1,200 |
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 | 27 bags | 1,080 sq ft |
| 50 sq ft | 22 bags | 1,100 sq ft |
| 75 sq ft | 15 bags | 1,125 sq ft |
| 90 sq ft | 12 bags | 1,080 sq ft |
| 106.8 sq ft | 11 bags | 1,175 sq ft |
What else matters here
Twelve hundred square feet of framing leaves 1,080 square feet of cavity, and eleven bags covers it with 95 square feet spare.
At this size the bags themselves become a handling problem before they become a money problem. Compressed batts expand as soon as the wrapper is cut, so open them where they are going to be installed rather than opening the pile at the door.
Check the batt width against the framing before ordering eleven bags of anything. A 15 inch batt in a 24 inch on center wall is wasted money and a 23 inch batt in a 16 inch wall has to be cut down the length of every single piece.
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 1200 square feet?
Eleven bags at 106.8 square feet per bag, covering 1,080 square feet of cavity.
Does batt width matter?
Yes. Batts come sized for 16 and 24 inch on center framing. The wrong width either leaves gaps or has to be trimmed on every piece, and both cost you more than buying the right one.
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.