Stucco bags = wall area × coat thickness ÷ 8.25 sq ft-inches per 80 lb bag, coat by coat. A 1,000 sq ft wall in classic 3-coat stucco over lath takes 116 bags with 10% extra: 50 for the scratch coat, 50 for the brown coat and 16 for the finish coat, plus 69 sheets of lath. The same wall in a 1-coat system at ⅜ in with a finish coat takes 66 bags. Pick the system, the wall behind it and the state, and the calculator gives bags per coat, lath, water and an installed cost range.
How the stucco is calculated
Quikrete's base coat data sheet gives coverage for an 80 lb bag at three thicknesses: 20 to 24 sq ft at ⅜ in, 15 to 18 sq ft at ½ in and 10 to 12 sq ft at ¾ in. All three rows are the same 7.5 to 9 sq ft-inches a bag, so coverage is that figure divided by the thickness. The calculator takes the middle, 8.25, for the base coats, and the finish coat sheet's 70 sq ft at ⅛ in (8.75) for the finish.
Bags per coat = wall area × (1 + waste) ÷ (8.25 ÷ coat thickness in inches), rounded up
Worked example: 1,000 sq ft, 10% extra. A ⅜ in coat covers 8.25 ÷ 0.375 = 22 sq ft a bag, so 1,000 × 1.1 ÷ 22 = 50 bags each for the scratch and brown coats. The ⅛ in finish covers 70 sq ft a bag: 1,100 ÷ 70 = 15.7, so 16 bags. Lath at 16 sq ft a sheet after laps is 69 sheets. Mixing takes 5½ quarts a base bag and 2 gallons a finish bag: 170 gallons in all. The coverage ranges in the data sheet give 108 to 126 bags, so the calculator shows that band too.
3-coat stucco: bags per coat
ASTM C926 Table 4 sets the nominal thickness of each coat by the wall behind it (vertical work):
| Wall behind | System | Coats | Total | Bags per 1,000 sq ft, 10% extra |
|---|---|---|---|---|
| Wood or steel frame with lath | 3-coat | ⅜, ⅜, ⅛ in | ⅞ in | 50, 50, 16 = 116 |
| Concrete block or brick | 3-coat | ¼, ¼, ⅛ in | ⅝ in | 34, 34, 16 = 84 |
| Concrete block or brick | 2-coat | ⅜, ⅛ in | ½ in | 50, 16 = 66 |
| Poured concrete | 2-coat | ¼, ⅛ in | ⅜ in | 34, 16 = 50 |
The IRC (R703.7.2) requires three coats over metal or wire lath and allows two over masonry or concrete. ASTM C926 adds that two-coat work is only for solid bases, so the calculator refuses 2-coat on a framed wall.
1-coat stucco
One-coat fiberglass reinforced stucco goes on in a single pass over lath and building paper, then gets a color or texture coat. Quikrete's One Coat data sheet has the same coverage table as its base coat, calls for at least ⅜ in over lath and wants control joints so no panel is over 144 sq ft. It also says only experienced or manufacturer-certified installers should apply it.
Lath, paper and trim
Over a frame wall the IRC calls for corrosion-resistant lath fastened with 1½ in 11-gage nails or ⅞ in 16-gage staples at 7 in or closer, two layers of Grade D paper in dry climates, and a weep screed at least 4 in above the ground with a 3½ in flange. The calculator counts lath sheets only for the frame wall, at 16 sq ft each (Donley Brick's figure for a sheet of wire mesh after laps). Add corner bead, screed and paper from your wall plan.
How long between coats
The IRC says the second coat of a three-coat job goes on no sooner than 48 hours after the first, and the finish coat not until 7 days after the second. In a two-coat job the finish waits 7 days after the base. Quikrete's data sheets add: mist-cure the base coat once it has set and do not apply below 40°F or above 100°F without cold or hot weather precautions.
Stucco cost per square foot
This Old House, quoting Homewyse (updated April 2026), puts traditional cement stucco at $6.36 to $9.66 a sq ft installed and one-coat systems at $3 to $9.75. HomeAdvisor (June 2026) gives $7 to $9 and says labor is 50 to 80% of the bill. The calculator applies those rates, splits them 65% labor and 35% materials, and scales them by your state, so 1,000 sq ft of 3-coat runs about $6,400 to $9,700 at US average prices. The "do it yourself" switch drops the labor share.
Mixing your own stucco
Quikrete's portland cement data sheet lists two ASTM C926 scratch and brown coat recipes by volume: 1 part cement, ½ part Type S lime and 4½ to 6 parts plaster sand, or 1 part cement, 1 part Type N masonry cement and 6 to 8 parts plaster sand. The bagged mix above saves you weighing sand.
Next: the rest of the wall
Blocks behind stucco need mortar, and a stone wainscot or accent wall on the same house is sized in the stone veneer calculator. Compare with siding, and see the brick calculator for masonry walls. For interior walls, plaster is the matching tool. Every block, brick and concrete tool is in the concrete and masonry calculators.