Insulation R-Value Calculator
Total R-value is your insulation's R-per-inch multiplied by its thickness. Pick a type and thickness below, and optionally your climate zone to compare against the DOE-recommended attic range.
The worksheet
insulation calculator6 in of fiberglass batt gives R-19.2.
| Insulation type | Fiberglass batt | |
| Typical R-per-inch | 3.2 | varies by manufacturer/product |
| Thickness | 6 in | |
| Total R-value = R/in × thickness | R-19.2 | |
| DOE-recommended attic range, Zone 5 | R49–R60 | energystar.gov insulation guidance, informational |
Insulation rated for the R-value above
6 in of fiberglass batt gives R-19.2. Match the product's printed R-value to the total you just calculated. Whole-attic or whole-wall jobs (especially spray foam) are usually worth a contractor quote.
Get matched with local insulation contractors for a free quoteFree, no obligation. We pass your numbers to suppliers so quotes come back accurate.Faced and unfaced batts in standard widths for walls, attics and floors.
Shop insulation battsDIY closed- and open-cell spray foam kits for smaller sealing and insulating jobs.
Shop spray foam kitsSome links are affiliate links: if you buy through them we may earn a commission at no extra cost to you. These are starting points, not engineering endorsements. Always confirm a product's rated snow load meets the design load above.
Notes
- R-per-inch varies by manufacturer and product line; check your product's printed/rated R-value for a precise spec rather than relying solely on a type average.
- Total R-value is the insulation's own rating; whole-wall or whole-attic effective R-value is usually lower once framing thermal bridging is accounted for. Your local energy code sets the as-built requirement.
- Adding insulation has diminishing returns: going from R-0 to R-30 saves far more energy than going from R-30 to R-60, because heat loss is roughly proportional to 1/R.
Notes & questions
01How many inches of insulation is R-30?+
It depends on the type: about 9–10 in of fiberglass batt (R≈3.2/in), roughly 5 in of closed-cell spray foam (R≈6.5/in), or about 6 in of rigid polyiso board (R≈6/in). Use the calculator above for your exact product's R-per-inch.
02What R-value do I need for my attic?+
The DOE's general guidance ranges from about R30–R49 in the mildest climate zones up to R49–R60 in the coldest. Select your climate zone above for the typical range, and confirm the exact requirement with your local energy code.