What R-value should I target?

That's set by the International Energy Conservation Code as amended by your state or local jurisdiction, and varies by climate zone and whether the work is new construction or a retrofit. Check your local building department or the DOE's climate zone map for the number that applies to your project — this calculator doesn't recommend one.

Why doesn't this calculator give me a coverage number?

Because federal law already puts it on your package. 16 CFR 460.12 requires every package of batts or blankets to state its R-value, length, width, thickness, and total square feet of insulation. That's the correct number for your specific product; anything this calculator asserted instead would be a guess competing with a legally required fact already printed on the package.

If I compress a batt into a smaller space, do I still get the labeled R-value?

No. A batt's labeled R-value assumes its full, uncompressed manufactured thickness. Squeezing an R-19 batt into a 3.5-inch wall cavity it wasn't made for gives you less than R-19 worth of performance, not the same R-value packed thinner. Match the batt's thickness to the cavity, not the other way around.

Do batts have the same settled-versus-installed thickness issue as blown-in insulation?

No — a batt is manufactured at one fixed thickness and tested for its labeled R-value at that thickness, so there's no settling to account for the way there is with loose-fill. Cutting waste around obstructions is a real, separate issue for batts that this calculator doesn't estimate.

How much extra should I buy for cutting waste?

There's no cited source for a typical batt cutting-waste percentage, so this calculator defaults to 0% rather than assert one. Cutting around studs, wiring, and boxes does produce real scrap — add your own margin in the waste field based on your layout's complexity.

How do I top up existing insulation with batts?

This calculator doesn't compute that directly. A second layer is sometimes installed perpendicular to the first to reduce seam gaps, but whether that's right for your situation, and how much R-value it adds, depends on your specific product — check your package's own instructions or an installer.

Do I need a vapor barrier or facing on batt insulation?

It depends on your climate and local code, not a universal rule — a facing on the wrong side of a wall can trap moisture instead of blocking it, and exposed faced batts sometimes need a code-compliant covering. Check your local building department and the product's own installation instructions.

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Batt Insulation Calculator

Every package of batt or blanket insulation sold in the US is legally required to state its R-value, length, width, thickness, and total square feet — printed right on the package under 16 CFR 460.12, a Federal Trade Commission regulation. That square-footage figure is the number this calculator uses, not one of its own: enter your area and your package's stated coverage, and get a bundle count. Batts don't have the settled-versus-installed-thickness question loose-fill insulation does — a batt is manufactured at one fixed thickness for its labeled R-value, not blown to a variable depth — but cutting waste around studs, joists, wiring, and boxes is real here in a way it isn't for an open attic pour. See the guidance below for that, for why compressing a batt costs you real R-value, and for what to check before you install.

Your room

LengthWidthUnit

Waste (%)Cutting batts to fit around studs, joists, wiring, and outlet boxes does produce real waste, unlike blown-in insulation poured into an open attic — but there's no cited source for a typical batt cutting-waste percentage, so this calculator doesn't assert one. Leave this at 0% to match the math exactly, or add your own margin for the cuts and scraps your specific layout will produce.

Bundle coverage (sq ft)Read this directly from your package's label — 16 CFR 460.12 requires every package of batts or blankets to state its total square footage. There's no standard figure to default to; use the number for your specific product.

Enter your room's dimensions above to see results.

How it's calculated

The calculator adds your waste percentage (0% by default — see below for why) to your area, then divides that by your package's stated coverage, rounding up to a whole bundle, since a partial bundle still has to be bought. That's the entire calculation. Nothing here estimates coverage or R-value — the coverage number is the one thing this calculator asks you to bring with you, read directly off your package's federally required label, because no calculator can know which product, thickness, or R-value you're buying.

Worked example

500 sq ft of wall area, with a package labeled 100 sq ft of coverage per bundle: at the 0% waste default, adjusted area stays 500 sq ft. Bundles needed = 500 ÷ 100 = 5 bundles exactly. Change the coverage number to whatever your actual package states — a different product, thickness, or R-value will give a different coverage figure and a different bundle count from the same 500 sq ft.

The label has the number — read it, don't calculate it

Every package of batts or blankets sold in the US carries its own label by federal law. 16 CFR 460.12 requires it to state R-value, length, width, thickness, and total square feet of insulation in the package — that last figure is this calculator's coverage number, and it's specific to the product in your hands, not a figure this page can look up for you. Read it off your actual package and enter it above.

Batts avoid one specific ambiguity loose-fill insulation has: there's no settled-versus-installed-thickness question, because a batt is manufactured at one fixed thickness and tested for its labeled R-value at that thickness, not blown to a variable depth that changes as it settles. But there's a related mistake that's specific to batts instead: compressing one into a cavity shallower than it's made for. A batt's labeled R-value assumes its full, uncompressed manufactured thickness — squeeze an R-19 batt (roughly 6 inches thick) into a 3.5-inch wall cavity, and you get less than R-19 worth of performance, not the same R-value in a thinner package. Match the batt's thickness to the cavity it's actually going into, not the other way around.

Cutting batts to fit is real, ordinary work — around studs and joists at the edges of a bay, around wiring and electrical boxes, and around blocking — and it produces real scrap in a way that pouring loose-fill into an open attic doesn't. This calculator doesn't add a waste percentage for that by default, because there's no cited source for a typical batt cutting-waste figure, but it's a real cost worth planning for on your own rather than assuming the bare divided number is exactly what you'll use.

If you're topping up existing insulation, this calculator doesn't compute that for you, the same as the blown-in calculator doesn't. A second layer of batts is sometimes installed perpendicular to the first to reduce gaps at the seams, but whether that's the right approach for your situation, and how much R-value it actually adds, depends on your specific product and installation — check your package's own instructions or an installer rather than estimating it here.

Batts commonly come faced (with a kraft paper or foil vapor barrier attached) or unfaced, and whether a vapor barrier is wanted, and on which side of the wall it should face, depends on your climate and your local code — a barrier on the wrong side can trap moisture instead of blocking it. Faced batts left exposed in some spaces also need a code-compliant covering, since the facing can be flammable. Check your local building department and the product's own instructions rather than assuming one facing choice is universally correct.

Target R-value itself is a code question this page doesn't answer. It's governed by the International Energy Conservation Code as amended by your state or local jurisdiction, and it varies by climate zone and by whether the work is new construction or a retrofit — the DOE publishes climate-zone recommendations, which are a useful reference but not the same thing as your jurisdiction's actual requirement. Confirm your target R-value with your local building department or the DOE's climate zone map first, then find a product labeled for that R-value, and enter its package's coverage number above.

Common mistakes

Compressing a batt into a cavity shallower than its manufactured thickness. A batt's labeled R-value assumes its full, uncompressed thickness — squeezing it into a shallower space gives you less R-value than the label states, not the same R-value in a thinner package.
Guessing at a target R-value instead of checking your local energy code. Target R-value is governed by the International Energy Conservation Code as amended locally, and varies by climate zone and whether it's new construction or a retrofit — check your local building department or the DOE's climate zone map, not a preset on this page.
Reading a coverage number off a different package, product, or R-value than the one you're actually buying. Coverage varies by thickness and R-value — the number that's correct for your job is on your own package.
Assuming batts need the same settled-versus-installed-thickness handling as blown-in insulation. They don't — a batt is manufactured at one fixed thickness — but cutting waste around obstructions is real here and this calculator doesn't estimate it for you.
Leaving gaps or compressing batts around wiring and boxes instead of cutting to fit properly. Gaps and compression both reduce real-world performance below what the labeled R-value promises.
Picking a facing (or no facing) without checking your climate and local code. A vapor barrier on the wrong side of a wall can trap moisture instead of blocking it, and exposed faced batts sometimes need a code-compliant covering.

Where the figures come from

16 CFR 460.12 requires every package of batts or blankets to state its R-value, length, width, thickness, and total square feet of insulation — that square-footage figure is this page's coverage number, read from the reader's own package rather than asserted here. 460.17 governs what an installer's receipt must disclose and separately warns against multiplying an R-per-inch figure by installed depth — a warning aimed primarily at loose-fill, where installed depth is a real variable; a batt's R-value is already tested at its one manufactured thickness, so that specific mistake mostly doesn't apply here (see the guidance below for the batt-specific version of it: compressing a batt into a shallower cavity than it's made for). Both are Federal Trade Commission trade regulation rules under 15 U.S.C. 41, the same pair cited on the blown-in insulation calculator — a legal disclosure requirement, not a measured physical property, per the distinction drawn in this site's methodology.

FAQ

What R-value should I target?: That's set by the International Energy Conservation Code as amended by your state or local jurisdiction, and varies by climate zone and whether the work is new construction or a retrofit. Check your local building department or the DOE's climate zone map for the number that applies to your project — this calculator doesn't recommend one.
Why doesn't this calculator give me a coverage number?: Because federal law already puts it on your package. 16 CFR 460.12 requires every package of batts or blankets to state its R-value, length, width, thickness, and total square feet of insulation. That's the correct number for your specific product; anything this calculator asserted instead would be a guess competing with a legally required fact already printed on the package.
If I compress a batt into a smaller space, do I still get the labeled R-value?: No. A batt's labeled R-value assumes its full, uncompressed manufactured thickness. Squeezing an R-19 batt into a 3.5-inch wall cavity it wasn't made for gives you less than R-19 worth of performance, not the same R-value packed thinner. Match the batt's thickness to the cavity, not the other way around.
Do batts have the same settled-versus-installed thickness issue as blown-in insulation?: No — a batt is manufactured at one fixed thickness and tested for its labeled R-value at that thickness, so there's no settling to account for the way there is with loose-fill. Cutting waste around obstructions is a real, separate issue for batts that this calculator doesn't estimate.
How much extra should I buy for cutting waste?: There's no cited source for a typical batt cutting-waste percentage, so this calculator defaults to 0% rather than assert one. Cutting around studs, wiring, and boxes does produce real scrap — add your own margin in the waste field based on your layout's complexity.
How do I top up existing insulation with batts?: This calculator doesn't compute that directly. A second layer is sometimes installed perpendicular to the first to reduce seam gaps, but whether that's right for your situation, and how much R-value it adds, depends on your specific product — check your package's own instructions or an installer.
Do I need a vapor barrier or facing on batt insulation?: It depends on your climate and local code, not a universal rule — a facing on the wrong side of a wall can trap moisture instead of blocking it, and exposed faced batts sometimes need a code-compliant covering. Check your local building department and the product's own installation instructions.