Free Calculator
R-Value Calculator (Depth → R-Value)
Enter your current attic insulation depth to get its R-value — and see how much more you need to reach the R-38 Florida standard.
Measure the depth of the insulation on your attic floor with a ruler.
Your estimated current R-value
R-15
Based on blown fiberglass (~R-2.5/inch), that's below the R-38 Florida standard — you'd add about 9.2″ more to get there.
R-per-inch varies by product — your insulation’s bag or coverage chart is the exact spec. Settling, gaps, and compression also lower real-world R-value.
Estimates are for planning only and based on typical Central Florida homes and 2026 pricing for blown-in fiberglass. Your exact price depends on attic access, existing insulation condition, and whether removal is needed — confirmed free during your inspection.
R-value is the measure of how well insulation resists heat flow — the higher the number, the better. But insulation is installed by depth (inches), so homeowners constantly need to convert between the two. This calculator converts between them for any common insulation material and shows the gap to Florida's R-38 target.
R-value per inch depends on the material — about R-2.2–2.7 for blown fiberglass, R-3.2–3.8 for cellulose, and R-6–7 for closed-cell spray foam — and it varies by product, so the manufacturer's coverage chart is the exact spec.
What goes into this estimate
Measure your depth. Use a ruler or tape at the attic floor to find the current loose-fill depth in inches.
Convert to R-value. We multiply depth by ~R-2.5 per inch (blown-in fiberglass).
Compare to R-38. We show how many inches — and how much R-value — you'd add to reach the Florida standard.
Frequently asked questions
How do I calculate R-value from insulation depth?
Multiply the depth in inches by the material's R-per-inch. Blown-in fiberglass is about R-2.5 per inch, so 10 inches ≈ R-25.
What R-value is my attic?
Measure the insulation depth and multiply by ~2.5 for blown-in fiberglass. This calculator does it for you and compares it to the R-38 Florida target.
How many inches is R-38?
It depends on the material: about 13–16 inches of blown fiberglass, ~11 inches of cellulose, or ~6 inches of closed-cell spray foam.
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