Insulation Calculator
Enter the area you're insulating and the coverage of one pack to find how many packs to buy.
How insulation quantity is calculated
Dividing the total area to insulate by the coverage area of a single pack (printed on the packaging) gives the exact number of packs needed with zero waste.
In practice, insulation gets cut around joists, pipes, and odd spaces, so a waste allowance (commonly 10%, more for complex spaces) is added before rounding up to a whole number of packs, since partial packs usually can't be purchased.
Frequently asked questions
Where do I find a pack's coverage area?
It's printed on the insulation packaging, usually alongside the R-value and roll or batt dimensions — multiply the roll's width by its length (or sum the areas of individual batts in a pack) if it's not stated directly.
Does this calculator account for the insulation's R-value?
No — this calculator only handles area and quantity. Make sure you've chosen a product with the R-value appropriate for your climate and application before using this to calculate how many packs to buy.
Should I subtract areas like windows and vents?
Yes, for wall insulation — subtract the area of any openings that won't be insulated from your total area for a more accurate pack count.