Insulation Calculator — R-Value, Coverage & Material Estimator
Match the target R-value to common insulation products, then see thickness, unit count, coverage, and a quick budget range. The IECC table below helps you cross-check wall, attic, and floor targets by climate zone.
R-value reference
| Material | R-value / inch |
|---|---|
| Batt fiberglass | R-3.14 |
| Blown fiberglass | R-2.2 |
| Blown cellulose | R-3.7 |
| Open-cell spray foam | R-3.7 |
| Closed-cell spray foam | R-6.5 |
| Rigid XPS | R-5.0 |
| Rigid EPS | R-4.0 |
IECC rule-of-thumb targets
| Zone | Wall | Attic | Floor |
|---|---|---|---|
| 1 | R-13 | R-30 | R-13 |
| 2 | R-13 | R-38 | R-13 |
| 3 | R-20 | R-38 | R-19 |
| 4 | R-20 or 13+5 | R-49 | R-19 |
| 5 | R-20 or 13+5 | R-49 to R-60 | R-30 |
| 6 | R-20+5 or 13+10 | R-49 to R-60 | R-30 |
| 7 | R-20+10 or 13+15 | R-60 | R-38 |
| 8 | R-20+15 or 13+20 | R-60 | R-38 |
Frequently Asked Questions
How does the calculator estimate bags or rolls?
It converts your target R-value into required thickness, then scales a typical coverage-per-unit value for that product type.
Should I price insulation by unit or by square foot?
Either works. Use price per unit when you have quoted bags, rolls, kits, or sheets. Use price per square foot when you have installed-price bids.
Why do climate-zone recommendations vary by assembly?
Roofs, walls, and floors lose heat differently. Code targets usually require higher attic R-values because heat loss is greatest there.
Keep the project moving
Use the free calculator for fast takeoffs, then plug the result into a reusable field template.
Need templates? Browse our professional template store — contracts, checklists, and planners from $17.