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InsulationCalculator
An attic floor covered in deep loose-fill insulation between exposed rafters, lit by a gable window

Attic · Walls · Crawl space · Garage · Spray foam

Know exactly how much insulation you need

Get the right R-value, how many bags to buy, what it will cost, and step-by-step guidance — whether you do it yourself or hire a professional.

  • Free to use
  • No email required
  • Every number explained

Start your insulation calculator

Get a personalized recommendation for your home.

sq ft

Your ZIP sets the climate zone these figures are based on

What you'll getAdd your ZIP to see these

Target
—
Material
—
DIY cost
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Calculate my insulation
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  • Takes about a minute

Where our numbers come from

Full methodology
  • U.S. Department of EnergyRecommended insulation levels for existing homes
  • ENERGY STARTarget R-value by climate zone
  • IECC climate zonesZone boundaries used to set your target
  • Manufacturer coverage dataBag coverage and R-value per inch

We reference these standards as sources. We are not affiliated with, endorsed by, or certified by any of them.

What are you insulating?

Each area has a different target R-value, a different install method, and a very different cost per square foot.

An attic floor filled with gray blown cellulose between wooden joists, gable vent at the far end

Attic

The biggest win in most homes. Depth is unlimited, so it is the cheapest R-value you can buy.

Calculate for attic
Pink fiberglass batts fitted between wall studs in a partially sheathed exterior wall

Walls

Cavity fill between studs. Capped by framing depth — a 2x4 wall tops out near R-15.

Calculate for walls
A crawl space with insulated floor joists above, ductwork, and a vapor barrier over the ground

Crawl space

Warmer floors and less humidity. Insulate the floor above, or the walls if sealed.

Calculate for crawl space
A garage interior with insulation visible between the ceiling joists and wall studs

Garage

Worth doing where there is living space above or behind it. Rarely worth it otherwise.

Calculate for garage

Recommended materials

Everything you need for a typical attic project

Quantities for a 1,240 sq ft attic adding R-45. The calculator produces this list for your own dimensions — including the air sealing and safety gear most estimates leave out.

Build my shopping list

Get a personalized list for your project

31 items for this project

Retailer buttons open a search at that store — exact products and pack sizes vary by location.

We don't show live retailer prices, because they change constantly and we have no approved product feed — the buttons take you to each retailer to check the current price yourself. Estimated material cost for this project is $610–$980, from our own assumptions rather than live retail pricing. Some retailer links are affiliate links, which may earn us a commission at no additional cost to you. As an Amazon Associate we earn from qualifying purchases. What we recommend is decided by the job, never by commission. Our affiliate disclosure

  • Current pricingchecked at the retailer
  • Chosen by usnot paid placements
  • Helps supportour free calculators

DIY installation in four steps

Most attics are a one-day job for two people. The order matters — each step gets harder once the next one is done.

Work out your target first
  1. A gloved hand applying foam sealant around copper pipes and a vent stack penetrating the attic floor

    Step 1: Air seal

    Foam and caulk the gaps around flues, wiring, plumbing, and top plates.

    Do this first. Once insulation is down you cannot reach any of it.

  2. A worker stapling a white rafter vent baffle between roof rafters above the insulation

    Step 2: Install baffles

    Staple a vent baffle into each rafter bay at the eaves.

    Blocked soffit vents cause moisture build-up and ice dams.

  3. A worker in a dust mask blowing loose-fill insulation across an attic floor through a wide hose

    Step 3: Add insulation

    Blow or lay to the depth your calculation calls for, working back toward the hatch.

    Set depth markers first — judging depth by eye is unreliable.

  4. A finished attic with an even, deep layer of loose-fill insulation across the whole floor

    Step 4: Check and clean up

    Walk the depth markers, fill low spots, then insulate the hatch itself.

    An uninsulated hatch undoes a surprising share of the work.

Based on the example above

Hire a pro, or do it yourself?

Attic insulation is one of the most cost-effective home upgrades — but the right choice depends on your attic, not on averages.

Attic area
1,240 sq ft
Current → target
R-15 → R-60
Depth to add
12.9"
A worker in a dust mask blowing loose-fill insulation across an attic floor through a wide hose

Professional installation

$2,050–$4,100

Installed, with material, labor and cleanup. Local quotes are the way to turn this range into a real price.

  • Low clearance or difficult attic access
  • Removing old, wet, or contaminated insulation
  • Air sealing and baffles done in the same visit
  • Contractor handles installation and cleanup
Get free local installer quotes

Free and no obligation. We pass your project to insulation professionals who cover your area; they contact you with prices. We are paid by them, which is what keeps the calculators free.

How to compare the quotes you get
A worker stapling a white rafter vent baffle between roof rafters above the insulation

Prefer to do it yourself?

$720–$1,300

Doing it yourself saves roughly $750–$3,380.

  • Accessible attic with a walkable floor
  • Blown-in or batts over existing insulation
  • Usually a weekend project for two people
Build my shopping listSee DIY installation guide

Both figures come from the same engine as the calculator. See our assumptions.

  • Real estimatesBased on your actual project size and R-value target, not a national average.
  • Unbiased guidanceWe tell you when DIY makes sense — and when your attic means it does not.
  • Nothing left outAir sealing, baffles, and safety gear are in the estimate, not discovered later.
  • A more comfortable homeFewer cold rooms and less draft. We show the cost, not a savings promise.

Not sure which option is right for you?

Read the full comparison — what the day actually looks like, when hiring out is worth it, and the middle option most people miss.

View comparison guide
A two-story suburban house at dusk with warm light in every window

Why proper insulation matters

Insulation is the cheapest lever most homes have. It is also the one where the difference between "some" and "enough" is easy to measure and easy to get wrong. Pick a benefit to see how the six common materials compare on it.

Pick a benefit to compare insulation materials on it

  • Less heat escaping in winter and less getting in during summer means the furnace and AC run less.

  • Fewer cold rooms, fewer drafts, and less temperature swing between floors.

  • Dense material damps airborne sound. Cellulose and mineral wool do this noticeably better than fiberglass.

  • A furnace that cycles less often lasts longer and needs less service.

R-value per inch

Nominal, at typical installed density — the same figures the calculator uses

  • Closed-cell foamR-6.5
  • Mineral woolR-4.0
  • Open-cell foamR-3.6
  • CelluloseR-3.5
  • Fiberglass battsR-3.2
  • Blown fiberglassR-2.5

Depth is what you are buying. Where you have room — an open attic — cost per unit of R matters far more than this ranking, and the two cheapest materials sit near the bottom of it. Where depth is capped, the ranking decides everything. The full R-value chart

How much air the material stops on its own

Relative ranking, not a measured rating

  • Closed-cell foamBest
  • Open-cell foamBest
  • CelluloseStrong
  • Blown fiberglassModerate
  • Mineral woolModerate
  • Fiberglass battsLimited

Only the two foams are air barriers in themselves. Everything else insulates but lets air through, so the gaps have to be sealed first — and in a draughty house that one step does more for comfort than the insulation laid on top of it. Why air sealing comes first

Airborne sound absorbed

Relative ranking, not a measured rating

  • Mineral woolBest
  • CelluloseStrong
  • Open-cell foamStrong
  • Fiberglass battsModerate
  • Blown fiberglassModerate
  • Closed-cell foamWeak

Sound wants density and a completely filled cavity. Note the flip: the material with the highest R-value per inch is the weakest of the six here, because rigid foam carries vibration rather than absorbing it. Cellulose vs fiberglass, compared

How well it holds its rated R-value over time

Relative ranking, not a measured rating

  • Closed-cell foamBest
  • Mineral woolBest
  • Open-cell foamStrong
  • Blown fiberglassStrong
  • CelluloseModerate
  • Fiberglass battsLimited

What saves the furnace is the R-value you still have in year fifteen, not the one printed on the bag. Cellulose settles 10–20%, so it goes in deeper than the target; batts sag and gap when they are cut short or stuffed around wiring. How we handle settling and real-world R

We deliberately don't put a dollar figure on annual savings. A credible number needs your actual energy use, local fuel prices, and equipment efficiency — not a square footage. Why we don't estimate savings.

Cost by attic size

Blown cellulose over bare joists in a cold climate, adding R-60. DIY covers material, air sealing supplies, blower rental, and safety gear.

Estimated attic insulation cost by floor area, adding R-60 with blown cellulose
Attic sizeBagsDIY totalProfessional
800 sq ft44$610–$1,100$1,750–$3,550
1,200 sq ft66$900–$1,600$2,650–$5,300
1,600 sq ft88$1,200–$2,050$3,550–$7,050
2,000 sq ft110$1,450–$2,500$4,400–$8,800

Professional pricing does not scale down linearly — mobilisation and minimum crew time dominate on a small job. Figures are generated by the same engine the calculator uses. See our assumptions.

Price my actual attic

Insulation types compared

Each material has a different R-value per inch, a different price, and a different job it is actually good at.

Close-up of stacked pink fiberglass batts showing the fiber texture

Fiberglass

R-2.5 – R-3.4 per inch

  • Cheapest per R-value
  • Batts need no equipment
  • Shrugs off water
  • Installed quality matters a lot
Learn about fiberglass
Close-up of loose cellulose insulation — gray shredded recycled paper

Cellulose

R-3.2 – R-3.8 per inch

  • Fills gaps batts leave
  • Mostly recycled paper
  • Best value for attics
  • Settles 10–20% over time
Learn about cellulose
Close-up of stacked mineral wool slabs showing their dense fibrous edge

Mineral wool

R-3.7 – R-4.2 per inch

  • Fire resistant
  • Best for sound
  • Handles damp locations
  • 2–3× the cost of fiberglass
Learn about mineral wool
Cream-colored spray foam expanded to fill the cavities between wall studs

Spray foam

R-3.6 – R-7.0 per inch

  • Air seals as it insulates
  • Highest R per inch
  • Best where depth is tight
  • Professional install only
Learn about spray foam

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Get accurate insulation results in about a minute

No email. No phone number. No lead form in front of your answer — just the numbers, and the arithmetic behind them.

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  • No personal informationYour privacy, always
  • Detailed results and shopping listMaterials, costs, and more
A cutaway model house with its attic framing exposed and insulation between the rafters, beside a calculator, a tape measure and a rolled batt of insulation

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