Insulation estimator

Enter the wall or attic area to cover, pick batts or blown insulation, and set your target R value. Package and bag counts use the epsilon safe ceiling BuildTrue applies everywhere, so an exact fit never orders one extra package. Switch between metric and imperial at any time. Your choice is remembered on this device. All results are estimates only.

Estimator

Insulation type

Wall or attic area (sq m)

Target R value (imperial R, as printed on Canadian product labels)

Waste and cutting allowance (percent)

Batt package coverage (sq m) per package, from the package label

Blown insulation R per inch, from the bag (cellulose is often about 3.7)

Blown bag coverage at R-20 (sq m) per bag, from the bag chart

Formulas: area with waste = area x (1 + waste / 100). Batts: packages = ceiling of (area with waste / package coverage). Blown: depth needed (in) = target R / R per inch. Coverage per bag at your target R scales from the R-20 chart value: coverage at target = bag coverage at R-20 x 20 / target R. Bags = ceiling of (area with waste / coverage at target). R value in metric: RSI = R / 5.678. All ceilings are epsilon safe.

Worked example (batts): Area 500 sq ft, waste 10 percent, package coverage 50 sq ft per package. Area with waste = 500 x 1.10 = 550 sq ft. Packages = 550 / 50 = 11 packages exactly. The metric defaults, 46.45152 sq m of area and 4.645152 sq m of package coverage, are the exact equivalents of 500 sq ft and 50 sq ft, so the defaults reproduce this example in both systems. Blown check: at target R-50 with R per inch 3.7, depth needed = 50 / 3.7 = 13.5 in (343 mm).

Estimates only. This is not a code compliance or energy modelling calculation. Stud cavities, joist spacing, settling, and provincial code requirements change real needs. Verify with the coverage chart on your product and a qualified professional before ordering.

Frequently asked questions

What R value should I target in Canada?

It depends on your province, climate zone, and whether the assembly is a wall, attic, or floor. Many Canadian attics are insulated to about R-50 or higher and many framed walls to about R-20 to R-24. Check your provincial code and energy program requirements before you buy.

Why does blown insulation need a depth?

Blown insulation gains R value with installed depth. Depth needed equals target R divided by the R per inch printed on the product bag. Settling reduces depth over time, so manufacturers publish settled coverage charts. Use the chart on your bag as the final word.

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