R-value is not the whole story
Air sealing, vapor control, moisture risk, thermal bridging and local code matter. Use manufacturer coverage for the exact product and thickness.
Example
For 600 square feet with a 5% waste allowance, adjusted area is 630 square feet. If one pack covers 50 square feet, the estimate rounds up to 13 packs.
Common mistakes
Do not use coverage from a different thickness or R-value. Also account for framing gaps, irregular cavities and offcuts.
Limitations
This calculator estimates pack count only. It does not determine building-code compliance, moisture strategy, ventilation, fire rating or installation quality.
Last reviewed: 2026-05-17