What should I enter for coverage per package?

Use the coverage printed for the exact product you plan to buy. If the label says one pack covers 5.6 m² or 60 ft², enter that number and match the unit system at the top of the page.

Should I subtract openings?

Subtract openings when they will stay uninsulated and you want a tighter purchase estimate. If you prefer a rougher buy, leave openings at 0 and rely on the waste percentage you choose.

Why is there leftover coverage?

Because the calculator rounds up to whole packages after applying waste. The leftover row shows how much extra coverage that round-up creates.

Does this calculator choose insulation type or code requirement?

No. It only does coverage math from your inputs. It does not determine required R-values or U-values, local code, rebates, climate guidance, or the best insulation product.

Insulation Calculator

Estimate how many insulation packs, rolls, or boards to buy for a wall, attic, floor, or ceiling job. Enter area directly or use a quick length x width helper, subtract openings, add waste, and see the rounded-up purchase count plus leftover coverage.

Units

Surface

Project size input

Gross area to insulate

ft²

Opening area to subtract

ft²

Coverage per package

ft²

Waste allowance

Result label

Examples

Enter values above to see results

How It Works

Formula

A_g = \begin{cases} A_d & \text{direct area entry} \\ L \cdot W & \text{length x width helper} \end{cases}

A_n = A_g - A_o

A_a = A_n \cdot \left(1 + \frac{w}{100}\right)

N = \left\lceil \frac{A_a}{A_p} \right\rceil

A_b = N \cdot A_p

A_l = A_b - A_a

$A_d$: Direct area entry(m²)
$L$: Length of the rectangular section(m)
$W$: Width of the rectangular section(m)
$A_g$: Gross area before openings(m²)
$A_o$: Opening area to subtract(m²)
$A_n$: Net area after openings(m²)
$w$: Waste allowance(%)
$A_a$: Adjusted area after waste(m²)
$A_p$: Coverage of one package(m²)
$N$: Packages to buy (rounded up)
$A_b$: Coverage purchased after rounding(m²)
$A_l$: Leftover coverage after rounding(m²)

Choose the surface you are planning for, then enter the job size either as a direct area or as length x width for a simple rectangle. The calculator subtracts any opening area you enter, multiplies the remaining area by your waste percentage, divides by the coverage of one package, and rounds up to whole packages. The supporting rows stay visible so you can see exactly how waste or package coverage changed the buy quantity.

Frequently Asked Questions

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