Insulation Calculator — Packages, Layers & Cost
Plan batts, rolls or loose-fill bags from product-label coverage. Combine surfaces, keep products separate and build a purchase list with your own quotes.
Insulation calculator · packages from product-label coverage
4 packages to buy1 product order · 2 surfaces / layers
Combine matching packages across surfaces. Keep different products and layers separate, and check both coverage limits for loose fill.
Plan your insulation orderStart with an editable example
These values demonstrate the calculation. Replace them with the exact label data for your product; they are not installation recommendations. Each example replaces the whole plan.
1. Exact products and packages
Use a separate entry for each thickness, facing or package size. Matching names alone do not merge products. Coverage and minimum depth must come from the same product and target R-value row.
Example insulation: batts / rolls, 60 sq ft per package. Price unknown. Illustrative coverage only.
2. Surfaces and layers
Measure only the surfaces receiving insulation. A second layer in a different material needs a separate entry and product. Identical layers multiply the net area.
Area 1: 120 sq ft. Area 2: 80 sq ft. One identical layer each, no excluded area and 0% extra reserve.
Your insulation purchase list
Dark green is planned coverage including your reserve; pale green is the remaining area equivalent. This is a quantity estimate, not a cutting or installation layout.
Example insulation
4 packages200 sq ft ÷ 60 sq ft/package = 3⅓ packages, rounded up to 4. Estimated surplus after reserve: 40 sq ft.
Illustrative values only — replace with the exact product label.
Enter your quotes
Missing quotes: Example insulation, delivery. This is not a complete project price.
How insulation quantities are calculated
Batts and rolls: pool before rounding
For each surface, subtract excluded area, multiply by identical layers, then multiply by (1 + additional reserve ÷ 100). Add the requirements of surfaces using the same product. Divide by the coverage of one exact package and round up. Different products remain separate purchase lines.
The default example needs (120 + 80) ÷ 60 = 3⅓ packages, so buy 4. The second example covers 200 sq ft twice using different products: each requires 4 packages, giving 8 in total.
Loose fill: why two label limits can matter
Coverage labels may state a maximum area per bag and a minimum bag count per 1,000 sq ft. If you enter both, this planner takes the larger unrounded requirement and rounds it up. Rounded label fields can differ slightly; meeting only the more generous field can understate the purchase.
In the synthetic attic example, 1,003 ÷ 59 gives exactly 17 bags, but 1,003 × 17 ÷ 1,000 gives 17.051. The order is therefore 18 bags. The entered minimum installed depth remains on the purchase list. These numbers do not establish a product’s R-value.
What this calculator does not determine
It does not select a required R-value, account for thermal bridges, choose vapor control or calculate an assembly’s code compliance. It does not infer existing insulation performance from depth, calculate spray-foam yield or promise energy savings. Follow the exact product instructions for installation, required density, depth and suitability.
Use 0% additional reserve when the entered coverage already includes the allowance you want. Surplus is an area equivalent at the entered label coverage, not proof that offcuts can be reused. Labor, equipment, tax and other materials need separate quotes unless included in the entered prices.
Source and related calculators
The Johns Manville Climate Pro attic card illustrates the distinction between coverage, minimum bags and installation depth. This independent tool does not embed that product’s table; use the current label for your actual product and location.
Planning the wall finish too? Use the drywall calculator for panels and the paint calculator for finish quantities.
