Insulation Calculator for Square Feet, Batts, Rolls & Boards
Estimate how much insulation you need from measured square feet, then convert the purchase area into whole batt, roll or rigid-board packages using the exact coverage printed on the product. The calculator does not choose an R-value for you.
Compare two product options using your calculated requirement
Compare two batts, rolls or rigid-board options only after confirming both satisfy the same R-value, assembly, thickness and installation requirements. Enter each product's labelled coverage per package and your actual price. The tool rounds up whole packages and compares the resulting material totals, not just package prices.
Adjusted insulation purchase area: Run or update the calculator above.
This comparison uses only the coverage/yield and price values you enter. It does not rank brands, fetch retailer data, include tax or delivery, or replace product specifications.
Continue your project estimate
Estimate drywall for the finished assembly →Insulation estimate in three steps
- Measure the wall, ceiling, floor or roof area you actually plan to insulate.
- Subtract excluded openings and apply only the extra-material percentage you intend to use.
- Enter the square-foot coverage printed on one package, roll, batt bundle or board package to get a whole-package count.
If you are using loose-fill material sold by bag yield at a target R-value, use the Blown-In Insulation Calculator instead.
How the insulation calculation works
Measure the surface you plan to insulate, subtract any openings you do not intend to cover, then add only the extra percentage appropriate to your layout and cutting plan.
net area = gross area − openings
purchase area = net area × (1 + extra %)
packages = ceiling(purchase area ÷ package coverage)
Use the exact package coverage
Insulation packages are not interchangeable units. Coverage varies by material, thickness, dimensions and packaging, so the calculator requires the square-foot coverage from the exact batt, roll or board product you plan to purchase.
R-value is a separate project decision
R-value measures resistance to heat flow, and recommended insulation levels vary with climate, building location and assembly. ENERGY STAR publishes climate-based guidance, but the appropriate requirement for a specific project should come from current code, project documents or qualified guidance rather than a hidden calculator default.
What about blown-in insulation?
This calculator is intentionally for products sold with a square-foot package coverage. Loose-fill and blown-in products use manufacturer-specific bag coverage that changes with installed depth, density and target R-value, so they should be calculated from the exact product chart rather than treated as the same purchase model. Spray foam may instead be priced by board foot at a specified thickness: the Spray Foam Insulation Cost Calculator explains how to convert that quote into a material-only price per installed square foot without confusing it with batt or roll package coverage.
Related calculators
Drywall Calculator · Stud Wall Calculator · Insulation package guide · Flooring Calculator
Package count does not choose the insulation specification
This calculator converts measured area into whole packages from the exact square-foot coverage you enter. It does not determine the required R-value, product thickness, vapor-control strategy or whether a batt, roll or board is appropriate for the assembly.
Use the package coverage printed for the selected product and target configuration. If the installation includes framing cavities with unusual spacing, obstructions or multiple layers, confirm how the manufacturer states coverage before ordering. Local energy-code and assembly requirements should be checked independently from the package arithmetic.
Example: a cheaper insulation package can cost more for the room
Suppose you have measured 1,050 sq ft of insulation purchase area after openings and your own cutting allowance. Product A covers a hypothetical 64 sq ft per package and is quoted at $55 per package. You would need ceiling(1,050 ÷ 64) = 17 packages, costing $935. Product B, at 70 sq ft per package and $64 per package, requires ceiling(1,050 ÷ 70) = 15 packages, costing $960. Although Product A is cheaper in this illustration, either may be unsuitable for the actual assembly.
This comparison is meaningful only when the two products satisfy the same specified R-value, cavity fit, layer count, product type and installation constraints. Do not rank incompatible insulation systems on coverage or package price alone. Neither hypothetical package coverage nor price is market data, a universal product specification or a recommended insulation type. Enter the actual specifications and quotes in the interactive comparator above.
Insulation purchasing checklist before checkout
Check the manufacturer's labelled square-foot coverage at the selected thickness and R-value, not a different package or construction method. Verify that batt width matches the actual cavity spacing, that rigid-board packs contain the expected number of sheets and that the selected product meets the assembly's moisture, fire and facing requirements. Some project areas must be planned as distinct layers or materials instead of combined into one package total.
If your supplier quote includes offcuts and whole-package rounding, do not add a second cutting percentage to that already-complete purchase quantity. For loose-fill or blown-in products, use the coverage chart at the required R-value rather than a generic square-foot-per-pack figure.
Example: openings change the area before package rounding
Suppose a group of wall surfaces measures 1,150 sq ft gross. If 150 sq ft of genuinely uninsulated openings can be excluded, net area is 1,000 sq ft. With an illustrative 5% cutting allowance, the purchase area is 1,050 sq ft. For a selected insulation package labelled at 64 sq ft of coverage, ceiling(1,050 ÷ 64) gives 17 whole packages.
If that same product instead covers 70 sq ft per package at the required specification, the result would be 15 packages. Neither coverage is a universal product fact: the R-value, thickness and manufacturer-stated installed coverage must match your selected assembly. Do not subtract openings when insulation will actually continue across them.
Compare full insulation package orders
Explore why a package with less coverage can still cost less after whole-package rounding, provided R-value and assembly requirements match.
Compare insulation types before buying
Read batts vs blown-in vs spray foam to distinguish R-value, air sealing, moisture hazards and product coverage before entering measured quantities above.