# Insulation Calculator

> Add the areas, then type the R-value per inch on your product and the R-value you want. You get the depth, the volume, the R-value of a depth you already have and the packages. 1,000 sq ft at R-3.5 per inch needs 10.9 in for R-38.

Canonical: https://receiptscanner.co/tools/insulation-calculator
Updated: 2026-10-28 · Sources re-checked by: 2027-10-28

This is a free interactive calculator that runs in the browser. Nothing you type is stored or sent. Results are estimates.

## How it works

R-value of a layer = depth in inches × the R-value per inch of the product. So depth needed = target R-value ÷ R per inch. Volume = area × depth ÷ 12 cubic feet, and cubic yards = cubic feet ÷ 27. Packages = area ÷ the coverage printed on the package, rounded up. R-values of separate layers add up. R per inch is a property of each product and is printed on the bag or batt label, so this page asks you for it instead of guessing. Insulation that is packed down gives less R per inch than its label.

**Depth needed for a target R-value, by R per inch**

| Target R-value | At R-3.0 per inch | At R-3.5 per inch | At R-4.0 per inch |
| --- | --- | --- | --- |
| R-13 | 4.3 in | 3.7 in | 3.3 in |
| R-19 | 6.3 in | 5.4 in | 4.8 in |
| R-30 | 10 in | 8.6 in | 7.5 in |
| R-38 | 12.7 in | 10.9 in | 9.5 in |
| R-49 | 16.3 in | 14 in | 12.3 in |

**Volume for 1,000 sq ft at different depths**

| Depth | Cubic feet | Cubic yards |
| --- | --- | --- |
| 4 in | 333 | 12.3 |
| 8 in | 667 | 24.7 |
| 12 in | 1,000 | 37 |
| 16 in | 1,333 | 49.4 |

## Worked example: a 1,000 sq ft attic, R-3.5 per inch, target R-38

1. Depth: 38 ÷ 3.5 = 10.86 in.
2. Volume: 1,000 × 10.86 ÷ 12 = 905 cubic feet, which is 33.5 cubic yards.
3. If there are already 12 in at R-3.5 per inch, that layer is 12 × 3.5 = R-42.
4. Packages that cover 100 sq ft each: 1,000 ÷ 100 = 10.

## FAQ

### What is R-value?
A measure of how well a material resists heat flow. A higher number insulates better. The R-values of layers add up, so two layers of R-19 make R-38.

### How do I calculate the depth for a given R-value?
Divide the R-value you want by the R-value per inch of your insulation. For R-38 at R-3.5 per inch that is 10.9 in.

### Where do I find R per inch?
On the bag, the batt label or the maker's data sheet. It differs between fiberglass, cellulose, mineral wool and foam, so use the figure for the product you buy.

### What R-value do I need?
It depends on your climate zone, the part of the house and local code. Use the figure from your building department or the product maker's zone map, and type it in as the target.

### Does compressed insulation lose R-value?
Yes. Squeezing a batt into a space that is too small, or packing loose fill too tightly, reduces its R per inch. Insulation works best fluffed to its full depth.

### How many packages of insulation do I need?
Divide the area by the coverage printed on one package and round up. Batts and rolls differ in width and length, so use the number on your package.

## Sources

- [R-value (insulation): thermal resistance, how it is measured and how layers add up](https://en.wikipedia.org/wiki/R-value_(insulation)) (checked 2026-10-28)

This calculator is an estimate for planning. Required R-values and installation methods depend on your climate and local code, so check them with your building department and follow the product maker's instructions.