Attic Insulation Calculator — R-Value, Inches & Bags

How to use

1. Measure attic area (footprint in sq ft) and average existing insulation depth.
2. Pick your climate zone — or override the target R-value yourself.
3. Choose your material: batts, blown fiberglass, blown cellulose or closed-cell foam.
4. Read extra inches needed, the R you are adding, and an approximate bag count.

About this tool

Most American attics are under-insulated, and the fix is cheaper than people fear — but only if you measure what is actually up there. Enter attic area and the current depth of insulation in inches, pick your climate zone, and this calculator sets the attic target (R-49 for zones 1–3, R-60 for zones 4–8, overridable), converts it to inches for your chosen material — fiberglass batts, blown fiberglass, blown cellulose or closed-cell spray foam — and reports exactly how many more inches you need. Blown cellulose gets an approximate bag count; spray foam comes out in board feet. Air-seal first: caulk top plates and penetrations before blowing anything, because insulation slows heat but does not stop air leaks. DIY-friendly math, entirely in your browser.

FAQ

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