How to use this calculator
Insulation quantity is label coverage arithmetic — but only if the coverage matches the product as installed. For blown-in insulation, coverage changes with the R-value and installed density on the product chart, so an area-only universal conversion would be wrong. This tool therefore asks for the coverage you read from the chart for your chosen product and condition.
Enter your own figures in the form above. A blank field is treated as missing — not as zero — so the tool will ask you to complete it. A genuine zero is accepted where it makes sense (for example, no HOA dues). Press Calculate for a breakdown, Load worked example to fill in the example below, or Reset to return to the defaults.
Formula and assumptions
Required area = area × (1 + waste %). Packages = required ÷ label coverage per package, rounded UP. Purchased coverage = packages × coverage. Cost = packages × pack price.
Worked example
Worked example: 1,000 ft², label coverage 50 ft² per bag, 10% waste. Required 1,100 ft²; 22 bags. If the product chart at a different R-value gave a different coverage, the bag count would change — re-enter the chart figure rather than reusing this one.
Use the Load worked example button above to reproduce this example in the form, then change one input at a time to see what drives the result.
Limitations and common mistakes
No R-value is recommended here, and no energy-savings, moisture, air-sealing or retrofit design is implied. Framing fraction, obstructions, settling (for blown-in) and installation quality all affect installed performance and are outside a quantity count.
Frequently asked questions
Why does blown-in coverage vary?
Because the same bag covers less area at a higher R-value (thicker install) or higher density. Always read the chart row for your target R-value.
Do batts need waste?
Yes for cutting around framing, wiring and obstructions. The waste figure is yours to set for the actual framing layout.
Does this tell me how much insulation I need for comfort?
No. That is an R-value and building-envelope question, not a package-count question. Quantity follows the R-value decision; it does not make it.
Sources
No external price, product or market data is used on this page. Every price, density, coverage and rate is a figure you enter, or a clearly labelled illustrative default in the form. Check product labels and supplier quotes for the figures that apply to your job.
Estimates only. Results from this calculator are not a loan offer, appraisal, engineering design, equipment selection or contractor quote.