How Much Insulation for 1,300 Square Feet?
Bags or rolls
11 bags
1,300 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 area1300 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls11 bags
| Gross area | 1,300 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 1,170 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) | 1,300 |
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 | 30 bags | 1,200 sq ft |
| 50 sq ft | 24 bags | 1,200 sq ft |
| 75 sq ft | 16 bags | 1,200 sq ft |
| 90 sq ft | 13 bags | 1,170 sq ft |
| 106.8 sq ft | 11 bags | 1,175 sq ft |
What else matters here
Eleven bags buys 1,175 square feet against 1,170 square feet of cavity. Five square feet of margin on a job with 1,170 square feet of cutting in it, which is to say none.
That is worth saying plainly, because a calculator that rounds up is still only rounding to the next whole bag, and the next whole bag is sometimes five square feet away. Anywhere the bought figure lands within about five percent of the cavity figure, buy one more.
Five percent is roughly what gets lost to normal work: batts cut short and thrown away, a bag that turns out to be a different width, a cavity that is out of square, a soaked batt from a leak nobody had found yet. Returning a sealed bag is easy at any big box store. Stopping the job and driving back is not.
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 1,300 square feet?
Eleven bags covers 1,175 square feet against 1,170 of cavity. That is only five square feet of margin, so buy twelve.
Should I buy extra insulation?
If the coverage bought is within about five percent of the cavity area, yes. Normal waste eats that, and an unopened bag is easy to return.
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.