Insulation calculator
Estimate insulated area, packages, air-sealing allowance, material range, labor range, and contractor total.
Home Project Estimates
Insulation calculator
May 9, 2026
1 area at 40 ft by 30 ft, target R-38.
Shopping list
- fiberglass blown30 packages
- Air-sealing foam, caulk, weatherstripping, bafflesAs needed
- Protective gearRespirator, gloves, eye protection
Assumptions
- Target is R-38
- 40 sq ft per package
- Old insulation removal and ventilation corrections are not included
- U.S. near average; pricing data: U.S. near average pricing
Planning estimate only. Not a contractor quote, engineering advice, or permit review.
1 area at 40 ft by 30 ft, target R-38.
Shopping list
- fiberglass blown30 packages
- Air-sealing foam, caulk, weatherstripping, bafflesAs needed
- Protective gearRespirator, gloves, eye protection
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Assumptions in this estimate
- Target is R-38
- 40 sq ft per package
- Old insulation removal and ventilation corrections are not included
- U.S. near average; pricing data: U.S. near average pricing
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How this is calculated
- Insulated area is length x width x number of areas.
- Package count divides area by package coverage and rounds up.
- Target R-value adjusts material and labor cost with a planning factor.
Assumption register
| Item | Low | Typical | High | Source |
|---|---|---|---|---|
| Attic R-value target | R-30 | R-38 | R-60 | ENERGY STAR insulation guidance Checked 2026-05-10 · high confidence |
| Package coverage | 25 | 40 | 75 | Homewyse home insulation cost calculator Checked 2026-05-10 · medium confidence |
| Installed insulation range | 1.3 | 3.6 | 13 | HomeGuide attic insulation cost guide Checked 2026-05-10 · low confidence |
Last reviewed: May 9, 2026. These values are planning defaults, not live prices.
Common mistakes
- Adding insulation before sealing air leaks.
- Blocking attic ventilation or covering recessed fixtures incorrectly.
- Ignoring old insulation removal, moisture, pests, or electrical hazards.
FAQ
Which R-value should you choose?
Use local climate-zone guidance and existing insulation depth. R-38 is a common attic planning baseline.
Does this include air sealing?
Yes, as a basic allowance. Major air sealing or ventilation work should be scoped separately.
Can this be used for walls?
It can estimate area and cost roughly, but wall cavities, access, and finish repair change the job.
Limitations
This calculator is for early budgeting only. Climate zone, ventilation, moisture, wiring, fixture clearance, and old insulation can require professional review.
This estimate is for planning only. It is not a contractor quote, engineering advice, or permit review.
Next step
Measure once more, compare the result with a real quote or shopping cart, and review the assumptions before buying materials.
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