Insulation calculator

Batt bags by R-value and framing, and blown-in bags and depth to reach your attic R-value.

Job

Job name (optional, for the printout)

Batts (walls, floors, ceilings)

Areas

Wall / area lengthftHeight / widthftHow many

Windows & doors to deductsq ft

Batt

Framing

Coverage per bagsq ftTypical — the bag label has the exact number.Calculated — type to override

Framing (not insulated)%Calculated — type to override

Poly vapor retarder (where code requires)

Blown-in attic

Attic floor areasq ft

Target R-valueR-49 to R-60 in most of the US (IECC).

Existing R-valueRoughly R-3 per inch of old fluffy insulation.

Material

R per inch (settled)Calculated — type to override

Settled densitylb/cu ftCalculated — type to override

Bag weightlbCalculated — type to override

Eaves needing bafflesft

Rafter spacingin

Materials list

Item	Qty	Unit price	Cost
Batts
R-13 (2×4 walls) batts, 16 in. on center900 sq ft of cavity at 40.1 sq ft/bag	24 bags	$	—
Blown-in
Cellulose (loose fill)13.2 in. over 1,000 sq ft	75 bags	$	—
Attic depth rulers	4 ea	$	—

How it works

Batts cover the cavities only: framing takes about 10% of a 16 in. wall and 6% at 24 in.
Blown-in depth = R-value to add ÷ R per inch; bags = area × depth × settled density ÷ bag weight. Always check the bag's coverage chart — products differ.
Add your supplier's unit prices to any line for a cost estimate; tax and markup are optional.

How to measure

Walls: length × height of exterior walls. Attic: the floor area of the space you're filling.

Estimates only. Coverage, sizes and waste vary by product and job — verify with the manufacturer's specs and your local building code before ordering.

Closing up the walls? Drywall calculator →

Wall / floor area	1,120 sq ft − 120 openings
Cavity area to fill	900 sq ft
Attic	1,000 sq ft: R-0 → R-49
Loose fill needed	13.2 in. settled, ≈ 1,766 lb