Floors & Walls
Insulation Calculator
Estimate batt or roll insulation packs from area, openings, waste and the product's coverage.
Enter your measurements
Results update as you type.
About this calculator
Enter the area to insulate — one figure or several walls and rooms — subtract openings like windows and doors, add a waste allowance, and enter the coverage per pack from the actual product label. The result is whole packs or rolls to buy, with purchased coverage shown separately. Use the Blown Insulation Calculator for loose-fill bags; this batt-and-roll model does not estimate spray foam.
How to measure
- Measure each wall, ceiling or floor separately; use the multiple-section mode to add their rectangular areas.
- Enter windows, doors and other uninsulated openings once as an area deduction.
- Use the actual pack or roll coverage for the product and R-value you selected.
How to use this calculator
- Measure the walls, floors or ceilings to insulate — one area or several sections.
- Subtract windows, doors and other openings.
- Choose a waste allowance for cuts and fitting.
- Enter the coverage per pack from the label of the product you are actually buying.
- Calculate for packs to buy.
Formula
Net area = total area − openings
Order area = net area × (1 + waste ÷ 100)
Packs = ⌈order area ÷ coverage per pack⌉, with coverage taken from the product label
Assumptions
- Batt/roll purchasing only. Use the separate Blown Insulation Calculator for loose fill; spray foam is outside this model.
- Coverage is the supplier's stated value for the exact product; it is not inferred from an R-value.
- Openings larger than the total area are rejected.
Common mistakes
- Using a coverage or yield for a different product, depth or application.
- Adding waste twice in both the measured quantity and allowance field.
- Treating a bag count as proof that the selected product is suitable for the installation.
Worked example
Try it: press “Load example” above the form.
100 m² with 10% waste is 110 m²; at 12 m² per roll, buy 10 rolls.
Limitations
No R-value recommendation, code compliance or whole-building heat-loss estimate. Quantity purchasing only.
Frequently asked questions
Does the calculator choose the required R-value?
No. It counts packages from the selected product’s coverage. Climate, assembly, moisture and local energy requirements determine the required thermal design.
Why must pack coverage match the product?
A pack count depends on its width, thickness, piece count and R-value. Use the printed coverage of the exact pack rather than assuming all batts cover the same area.
What does the worked example show?
100 m² with 10% waste is 110 m²; at 12 m² per roll, buy 10 rolls.
Which assumptions should I check before using the result?
No R-value recommendation, code compliance or whole-building heat-loss estimate. Quantity purchasing only.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
- Owens Corning: product coverage charts
Coverage varies by product, target depth and region. No manufacturer yield is supplied as a preset.
Calculation documentation · Updated 2026-11-11 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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