Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Bags / bundles needed
30
Material cost
$1,440
Estimated annual savings
$343
Payback (years)
4.2
Heat loss reduction (%)
61.2
10-year net
$1,989
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter area to insulate (sq ft).
- 2Enter current r-value.
- 3Enter target r-value.
- 4Enter coverage per bag/bundle (sq ft).
- 5Enter price per bag/bundle ($).
- 6Enter annual heating + cooling bill ($).
- 7Read your bags / bundles needed on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Going from R-19 to R-49 in an attic cuts conductive loss through that surface by roughly 60%. The upgrade usually pays back fastest in cold, high-fuel-cost climates.
Worked example
Using the values the calculator loads with:
Inputs
- Area to insulate: 1200 sq ft
- Current R-value: 19
- Target R-value: 49
- Coverage per bag/bundle: 40 sq ft
- Price per bag/bundle: 48 $
- Annual heating + cooling bill: 1600 $
Results
- Bags / bundles needed: 30
- Material cost: $1,440
- Estimated annual savings: $343
- Payback (years): 4.2
- Heat loss reduction (%): 61.2
- 10-year net: $1,989
What each field means
Inputs
- Area to insulate (sq ft)
- The area to insulate used in the calculation, measured in sq ft. Starts at 1200 sq ft so you have a working example on load.
- Current R-value
- The current r-value used in the calculation. Starts at 19 so you have a working example on load. Accepted range: 0–60.
- Target R-value
- The target r-value used in the calculation. Starts at 49 so you have a working example on load. Accepted range: 5–80.
- Coverage per bag/bundle (sq ft)
- The coverage per bag/bundle used in the calculation, measured in sq ft. Starts at 40 sq ft so you have a working example on load.
- Price per bag/bundle ($)
- The price per bag/bundle used in the calculation, measured in $. Starts at 48 $ so you have a working example on load.
- Annual heating + cooling bill ($)
- The annual heating + cooling bill used in the calculation, measured in $. Starts at 1600 $ so you have a working example on load.
Results
- Bags / bundles needed
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Material cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Estimated annual savings
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Payback (years)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Heat loss reduction (%)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- 10-year net
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the insulation r-value & batt calculator work?
Going from R-19 to R-49 in an attic cuts conductive loss through that surface by roughly 60%. The upgrade usually pays back fastest in cold, high-fuel-cost climates. The underlying maths is: Batts = area ÷ coverage per bag; loss ∝ 1 ÷ R-value.
What do I need to enter?
6 values: area to insulate, current r-value, target r-value, coverage per bag/bundle, price per bag/bundle, and annual heating + cooling bill. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the bags / bundles needed result mean?
It is returned as a whole number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Insulation Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/insulation-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/insulation-calculator" target="_blank" rel="noopener">Insulation Calculator — RevenueLab</a> (2026).</p>
Source: [Insulation Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/insulation-calculator) (2026).