Stucco Calculator — bags by the coat, and plaster by the wall
Bags of base coat and finish coat from the wall area and the coat thickness at the data sheet's coverage, and cement and sand for site-mixed plaster.
Bags of base coat and finish coat from the wall area and the coat thicknesses, at the coverage the bag’s data sheet states — and, for site-mixed cement plaster, the wet volume and the cement and sand it takes.
| Wall area | — |
|---|---|
| Base coat | — |
| Finish coat | — |
| All bags | — |
| Base coat by yield | — |
| Plaster, wet volume | — |
|---|---|
| Cement | — |
| Sand | — |
The bag count comes from the data sheet, and the data sheet gives a range. QUIKRETE’s scratch-and-brown base coat (No. 1139) covers 20 to 24 square feet per 80 lb bag at ⅜ inch, 15 to 18 at ½, 10 to 12 at ¾. That is one bag spread thinner or thicker, which is why the page scales the coverage with the thickness. The finish coat (No. 1201/1202) covers about 70 square feet at ⅛ inch. The page prints the count at the low end of the range, which is the number to order, and shows the high end beside it. Another maker’s bag has another figure. The coverage fields are there to take it.
Three coats are ¾ inch of base, and that is where the bags go. A traditional three-coat system is a ⅜-inch scratch coat, a ⅜-inch brown coat and a thin finish. Two-coat and one-coat systems put ⅜ inch of base on and finish over it. On a thousand square feet of wall the difference between the systems is roughly fifty bags of base at the data sheet’s low end. That is a pallet or so, and worth knowing before the order goes in. Which system the wall gets is a question for the lath and the substrate, with ASTM C926 governing the application. This page only counts the bags.
Site-mixed plaster is a volume, then a split. Area times thickness, with the same waste the bags carry, is the wet volume on the wall. The dry cement and sand bulk larger than that, and the 1.3 factor here is a common estimating allowance, editable. Split the dry volume by the mix, where 1:4 is one part cement to four of sand, so cement is a fifth of it. The four ratios offered are common proportions, not a mix design; the specification for the wall governs. A bag of portland cement is 94 lb and one cubic foot by convention. Metric readers get the same volumes in cubic metres; a 50 kg bag is not a fixed volume, so the page does not count those.
Net area = length × height − doors × 21 ft² − windows × 15 ft² (nominal openings, the figures the siding and drywall pages use); bags = ceil(net × (1 + waste) × (thickness ÷ ⅜") ÷ coverage). Base coat coverage 20–24 ft² per 80 lb bag at ⅜" and yield 0.75 ft³ per bag: QUIKRETE Scratch and Brown Base Coat Stucco No. 1139 data sheet (rev. Oct 2021); finish coat 70 ft² at ⅛": QUIKRETE Stucco Selector Guide, No. 1201/1202. Wet plaster volume = area with waste × thickness; dry = wet × factor (1.3 is an estimating allowance, not a specification, and the 1:3–1:6 ratios are common proportions rather than a mix design); cement = dry ÷ (1 + sand parts); a 94 lb bag of portland cement = 1 ft³ (US sack convention).
Worked example
1,080 ft² of wall with a door and six windows, three-coat stucco: how many bags?
- Net area 1,080 − 21 − 90 = 969 ft²; with 10% waste, 1,066 ft².
- Three coats are ¾" of base, twice the ⅜" data-sheet thickness: 1,066 × 2 ÷ 20 = 106.6, so 107 bags (89 at the 24 ft² end of the range).
- Finish at 70 ft² a bag: 1,066 ÷ 70 = 15.2, so 16 bags. 123 bags in all, 9,840 lb.
About 107 bags of base coat and 16 of finish — three pallets. The yield cross-check (0.75 ft³ a bag) lands at 89, the high end of the coverage range.
20 values on this page were driven in a browser and compared with independently derived figures on 2026-09-06 (661 values across 69 calculators site-wide).
Questions
How many square feet does a bag of stucco cover?
An 80 lb bag of base coat covers 20–24 ft² at ⅜" (QUIKRETE No. 1139 data sheet); a three-coat system is ¾" of base, so 10–12 ft² a bag. Finish coat covers about 70 ft² at ⅛".
How thick is stucco?
Three-coat: ⅜" scratch + ⅜" brown + ⅛" finish, ⅞" in all. Two-coat and one-coat systems put ⅜" of base under the finish. ASTM C926 sets the application.