How Much Insulation for a 12x16 Room?
Bags or rolls
4 bags
The four walls of a 12 by 16 room at 8 foot ceiling height, 56 linear feet of wall, framed at 16 inches on center.
When the figures look right, the insulation material list downloads as a real PDF with your business details on it, built inside your own browser. Nothing you type is uploaded anywhere.
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 area448 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls4 bags
| Gross area | 448 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 403 sq ft |
| Bags at 106.8 sq ft | 4 |
| Coverage bought | 427 sq ft |
The material list this produces
| Insulation batts, bags | 4 |
|---|---|
| Vapor retarder, sq ft (if required) | 448 |
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 | 11 bags | 440 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 | 4 bags | 427 sq ft |
What else matters here
Fifty six feet of wall at eight feet tall is 448 square feet gross, 403 of cavity, four bags.
What the count does not tell you is which batt. A 2 by 4 wall has a 3.5 inch cavity and takes R-13 or, in a higher density product, R-15. A 2 by 6 wall has 5.5 inches and takes R-19 or R-21. Putting an R-19 batt in a 2 by 4 wall does not give you R-19, because compressing fiberglass loses most of the gain you paid for.
Coverage per bag moves with all of this. An R-13 bag covers a lot more wall than an R-21 bag, so the number on this page is right for the default coverage and wrong for anything else. Read the square footage off the bag you are buying and put it in the coverage field.
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 a 12x16 room?
Four bags for all four walls at 8 feet high, based on 448 square feet of wall and 403 of cavity.
What R value goes in a 2x4 wall?
R-13, or R-15 in a high density batt. R-19 is made for a 2 by 6 wall and loses most of its value if you squeeze it into 3.5 inches.
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.