How much stucco do you need? Coverage math that holds up

Start from thickness, not from the bag

ASTM C926 sets the nominal plaster thicknesses: over metal lath, 7/8 inch total in three coats — a 3/8-inch scratch coat, a 3/8-inch brown coat and a roughly 1/8-inch finish. Over solid concrete or masonry, the base is thinner, typically 3/8 to 5/8 inch total. Thickness moves your quantity more than any other decision, so settle it (from the spec or the permit set) before counting bags.

The math

Coverage is volume divided by thickness — the same arithmetic every manufacturer's yield table is built on.

• →One cubic foot of mixed plaster at 3/8 inch thick covers about 32 sq ft.
• →One cubic foot at the full 7/8 inch covers about 13.7 sq ft.
• →One cubic yard (27 cu ft) at 7/8 inch covers about 370 sq ft.
• →Wall area = length × height, minus openings larger than a door.
• →Add 10–15% for waste, the plaster keyed into the lath, and an uneven substrate.

A worked example

Say the job is 1,200 sq ft of wall over metal lath at 7/8 inch. The placed volume is 1,200 sq ft × 0.073 ft of thickness ≈ 88 cubic feet — about 3.2 cubic yards of mixed plaster — call it 3.5 to 3.7 yards once waste is in. From there the bag count depends entirely on which product you are mixing, which is the data sheet's job, not a rule of thumb's.

Why we don't quote per-bag coverage

Yield differs between a sanded pre-blend, a fiber one-coat base and a site mix of portland and sand — and between manufacturers of each. The honest number is on the bag's data sheet (Quikrete publishes one per product line, linked below; every brand we stock does the same). Bring the wall area, the substrate and the spec to the counter and we size the order against the actual product, with the waste margin that fits the crew and the wall.

Sources & further reading

• ASTM C926 — Standard Specification for Application of Portland Cement-Based Plaster
• Quikrete — base coat stucco product line and data sheets
• Quikrete — finish coat stucco product line and data sheets

Guidance only. Your project spec, the product data sheet and the local building department govern the job — bring the spec to the counter and we size the order with you.