Attic size and R-values in, bag count and installed cost out — for blown cellulose or fiberglass. Then send it straight into a quote.
Ballpark, not gospel. Bag coverage varies by brand and blower settings — always check the coverage chart on the bag you're actually buying before quoting.
Straight answers, no fluff. Then run your own numbers above.
It depends on your attic size and how much R-value you're adding. A 1,200 sq ft attic going from R-11 to R-38 needs roughly 30–35 bags of cellulose or 20–25 bags of fiberglass. The calculator above works it out from your exact numbers, plus 10% extra.
The DOE recommends R-38 (about 10–14 inches of blown insulation) for most of the US, and R-49 in the coldest zones. Check your local energy code — it varies by climate zone.
Cellulose is cheaper per R-value and fills gaps well, but settles over time. Fiberglass doesn't settle and is lighter on old ceilings. Both hit the same R-values; the choice usually comes down to price and what your supplier stocks.
Pro-installed blown insulation runs $1.50–$3.50 per sq ft in 2026 — so $1,800–$4,200 for a typical 1,200 sq ft attic. DIY with a free loaner blower cuts that roughly in half, to materials plus a weekend.
Got your numbers? Turn this estimate into a professional insulation quote and send it before you leave the job site.