Insulation calculator
Estimate new insulation or attic top-up needs from existing depth or R-value, with packages, air-sealing allowance, material range, labor range, and contractor total.
Home Project Estimates
Insulation calculator
May 15, 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.
Calculator setup
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
Take this estimate with you
Connect Google Drive to keep saved estimates in your Google account.
Shared links include the current inputs and unit setting. Saved estimates stay local unless you enable Google Drive sync.
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
No saved estimates yet.
What this calculator estimates
This insulation calculator starts from the measurements and options you enter, then estimates material quantity, waste, cost ranges, labor ranges, and a starter shopping list.
Results adapt to the selected region and unit settings, so the estimate is not locked to one market or measurement system.
Report confusing results, missing options, or assumptions that look off.
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.
- Attic top-up mode subtracts existing R-value from the target, then estimates the added R-value and approximate added depth.
Assumption register
| Item | Low | Typical | High | Source |
|---|---|---|---|---|
| Attic R-value target | R-30 | R-38 | R-60 | ENERGY STAR insulation guidance Checked 2026-06-21 · high confidence |
| Package coverage | 25 | 40 | 75 | Homewyse home insulation cost calculator Checked 2026-06-21 · medium confidence |
| Installed insulation range | 1.3 | 3.6 | 13 | Homewyse home insulation installed benchmark Checked 2026-06-21 · low confidence |
Last reviewed: May 15, 2026. These values are planning defaults, not live prices.
Common mistakes
- Adding insulation before sealing air leaks.
- Topping up an attic without measuring the existing insulation depth or R-value.
- 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.
When should you use attic top-up mode?
Use attic top-up mode when you already have insulation and want to estimate only the extra R-value and depth needed to reach the selected target.
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.
Can this insulation calculator estimate cost by region?
Yes. The calculator uses the selected region and unit settings to adapt quantities, cost ranges, labor ranges, and assumptions.
How should you use the result before buying materials?
Use the result as a planning estimate, then compare it with a current supplier cart, contractor quote, or local project conditions before committing.
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.
Read the how much insulation do I need guide
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