Calculate exactly how much attic insulation you need โ bags, rolls, thickness, and cost. Works for blown in cellulose, blown in fiberglass, and fiberglass batts. Free and instant.
Choose your insulation material, then enter your attic dimensions.
An attic insulation calculator is a free online tool that helps you determine exactly how much insulation material you need for your attic. It takes your attic dimensions, your climate zone, and your desired R-value, then calculates the number of bags or rolls, the required thickness in inches, and the estimated attic insulation cost.
Your attic is the most important area in your home to insulate properly. Up to 25% of your home's heat escapes through an under-insulated attic, which means proper insulation can significantly reduce your energy bills. Our attic insulation cost calculator helps you plan the project accurately โ whether you are adding insulation for the first time, topping up existing insulation, or replacing old material entirely.
This calculator supports the three most common attic insulation materials: blown in cellulose (the most popular for DIY attic projects), blown in fiberglass (lightweight and moisture-resistant), and fiberglass batts (the easiest to install by hand). Many homeowners search for attic insulation blow, attic insulation blow in, blow in insulation attic, blow insulation in attic, blown attic insulation, or blown insulation for attic projects โ these all refer to the same technique of using a blower machine to install loose-fill insulation across your attic floor. For spray foam attic projects, try our dedicated spray foam insulation calculator.
Learning how to calculate attic insulation is straightforward. Our attic insulation calculator automates the process, but here is the step-by-step math behind it:
Measure the length and width of your attic floor. For irregular shapes, break the attic into rectangles and add them together. Multiply length by width to get your total attic square footage. This number is the foundation for any estimate attic insulation calculation โ every bag count and cost number flows from it. If you're asking "how much insulation in attic do I need?", the answer always starts with this square footage measurement.
Your target R-value depends on your climate zone. The Department of Energy recommends R-30 to R-60 for attics, with most homeowners targeting R-49. Our insulation calculator attic tool helps you pick the right value based on where you live.
Each attic insulation material has a different R-value per inch, which determines the required thickness and number of bags:
| Material | R-Value/Inch | Thickness for R-49 | Cost per Sq Ft | Coverage at R-49 |
|---|---|---|---|---|
| Blown-In Cellulose | R-3.5 | 14.0 inches | $0.80 โ $1.50 | ~11 sq ft/bag |
| Blown-In Fiberglass | R-2.5 | 19.6 inches | $0.70 โ $1.30 | ~15 sq ft/bag |
| Fiberglass Batts | R-3.2 | 15.3 inches | $0.50 โ $1.50 | ~29 sq ft/roll |
Our calculate attic insulation tool divides your attic square footage by the coverage per bag or roll at your target R-value. It then estimates cost by multiplying the square footage by the material's cost per square foot. For blown in materials, many retailers including Home Depot and Lowe's sell popular brands like Greenfiber cellulose and Owens Corning AttiCat fiberglass, often with free blower rental when you buy enough bags.
An attic insulation calculator is essential whenever you are planning to improve or install attic insulation. Here are the most common scenarios where homeowners rely on our attic insulation cost calculator:
Understanding attic insulation cost helps you budget accurately. Here is a complete cost breakdown for a typical attic project, including both DIY and professional installation pricing:
| Material & Method | Cost per Sq Ft | 1,000 Sq Ft Attic | 1,500 Sq Ft Attic |
|---|---|---|---|
| Cellulose Blown-In (DIY) | $0.80 โ $1.50 | $800 โ $1,500 | $1,200 โ $2,250 |
| Cellulose Blown-In (Pro) | $1.50 โ $2.50 | $1,500 โ $2,500 | $2,250 โ $3,750 |
| Fiberglass Blown-In (DIY) | $0.70 โ $1.30 | $700 โ $1,300 | $1,050 โ $1,950 |
| Fiberglass Blown-In (Pro) | $1.30 โ $2.30 | $1,300 โ $2,300 | $1,950 โ $3,450 |
| Fiberglass Batts (DIY) | $0.50 โ $1.50 | $500 โ $1,500 | $750 โ $2,250 |
| Spray Foam โ Open Cell (Pro) | $1.50 โ $3.00 | $1,500 โ $3,000 | $2,250 โ $4,500 |
The attic insulation cost you pay depends on your attic size, chosen material, and whether you DIY or hire a pro. For most homeowners, DIY blown in cellulose offers the best balance of cost and performance. The blown in attic insulation cost for a typical 1,000 sq ft attic at R-49 is $800-$1,500 (DIY materials) or $1,500-$2,500 (professional installation). Our attic insulation cost calculator gives you a realistic estimate based on your specific dimensions.
Choosing the right material for your attic depends on your budget, climate, and whether you are doing it yourself. Here is how the three most popular attic insulation options compare:
| Feature | Blown-In Cellulose | Blown-In Fiberglass | Fiberglass Batts |
|---|---|---|---|
| R-Value/Inch | R-3.5 (best) | R-2.5 | R-3.2 |
| Thickness for R-49 | 14.0" (thinnest) | 19.6" | 15.3" |
| DIY Cost (1,000 sq ft) | $800 โ $1,500 | $700 โ $1,300 | $500 โ $1,500 |
| Gap Coverage | Excellent โ fills everything | Good | Moderate โ gaps at joists |
| Moisture Resistance | Poor โ absorbs water | Excellent | Good (with facing) |
| Settling Over Time | 15-20% settling | Minimal | None |
| DIY Difficulty | Easy (machine needed) | Easy (machine needed) | Easiest (no machine) |
| Best For | Most attics | Humid climates | Small/simple attics |
| Brand Examples | Greenfiber, Applegate | Owens Corning AttiCat, CertainTeed InsulSafe | Owens Corning, Johns Manville |
For most attic insulation projects, blown in cellulose is the best overall choice โ it has the highest R-value per inch, fills around obstacles like pipes and wires, and is affordable for DIY. If your attic is in a humid area, blown in fiberglass is the safer bet because it does not absorb moisture. Fiberglass batts are the simplest for very small or straightforward attics where you can lay rolls between joists without a machine.
Adding attic insulation is one of the most rewarding DIY home improvement projects. Most homeowners can complete a 1,000 sq ft attic in 2-4 hours with a helper. Here is what you need to know:
The right R-value for your attic insulation depends on your US climate zone. Here is a quick reference:
| Climate Zone | States (Examples) | Recommended R-Value | Cellulose Thickness | Fiberglass Thickness |
|---|---|---|---|---|
| Zones 1-3 (South) | FL, TX, AZ, GA, LA | R-30 to R-49 | 8.6" โ 14.0" | 12.0" โ 19.6" |
| Zones 4-5 (Central) | VA, TN, KS, CO, OR | R-38 to R-60 | 10.9" โ 17.1" | 15.2" โ 24.0" |
| Zones 6-7 (North) | MN, WI, MI, NY, ME | R-49 to R-60 | 14.0" โ 17.1" | 19.6" โ 24.0" |
Not sure which zone you are in? A general rule: if your winters are mild, aim for R-30 to R-38. If you get freezing winters, go for R-49. If you live in the coldest states, R-60 is worth the extra cost. Our attic insulation calculator helps you see the cost difference between R-values โ often the jump from R-38 to R-49 is only $200-$400 more for a typical attic, making R-49 the sweet spot for most homeowners.
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