Insulation Calculator
Free insulation calculator—estimate packs from area, coverage per pack, and waste.
Results
13Packs to buy
- 12.5Exact packs
How it works
Packs = (area × (1 + waste%)) ÷ coverage per pack. We ceil to whole packs.
Worked example
Example: 1,000 sq ft, 88 sq ft/pack, 10% waste → 13 packs.
Read the bag
Batt and roll bags list square-foot coverage for a given thickness and width. Enter that coverage number.
Cavity vs continuous
This sizes area coverage only. R-value and continuous exterior insulation are specification choices, not piece counts.
Waste
Odd framing and cutouts increase waste. 10% is a common starting point.
Frequently asked questions
How many packs of insulation do I need?
Divide wall or attic area by the coverage on the package, then add waste. Use this calculator with those two numbers.
Batts or blown-in?
This tool is for packaged batts/rolls. Blown-in uses bags by volume—follow the manufacturer’s bag chart.
Does this include vapor barrier?
No. Facing, vapor retarders, and air sealing are separate materials.
Estimates only. Verify coverage rates and local requirements before purchasing materials. Not a substitute for professional advice.