Stucco Calculator
Estimate 3-coat stucco: bags of scratch, brown, and finish coat, or field-mixed cement and sand, from your wall area. Per ASTM C926 / SMA thicknesses. Free, no sign-up.
What to calculate next
Tools commonly used alongside this calculation
Mortar Calculator
Estimate mortar for brick and block: bags of premixed mortar, or masonry cement and sand, by unit count or wall area. Includes Type N, S, M, O mix ratios per ASTM C270. Free, no sign-up.
Concrete Block (CMU) Calculator
Estimate a CMU wall from its size: block count, mortar (cement + sand), core-fill grout, and rebar for 6, 8, and 12 in units per NCMA TEK 14-13. Subtract openings and add a waste allowance. Free, no sign-up.
Concrete Calculator
Calculate concrete for slabs, footings, walls, columns, and sonotubes. Add pours to get total cubic yards, the number of 40/60/80 lb bags, a waste allowance, and ready-mix cost. Free, no sign-up.
Explanation
Portland cement stucco is a three-coat plaster: a scratch coat, a brown coat, and a finish coat, each with its own thickness and bag coverage. Because the coats cover at different rates, a single “square feet” number does not tell you how many bags to buy — you have to size each coat. This calculator does that from your wall area, for the full 3-coat system, a 2-coat system, or a finish-only re-coat, and gives you premixed bag counts or the field-mixed cement and sand for the base.
How much stucco a wall takes
Each coat is estimated from the net wall area — the gross face area minus doors and windows — divided by that coat’s coverage per bag, with a waste allowance added first:
If you mix your own base coat, the scratch and brown are a 3:1 sand-to-cement plaster: the base volume is the net area times the base thickness, and roughly one 94 lb sack of portland cement with three cubic feet of sand yields about three cubic feet of plaster. The same 3:1 base is the cousin of the masonry mortar sized by the mortar calculator.
| Coat | Thickness | Coverage |
|---|---|---|
| Scratch coat (base) | 3⁄8 in | ≈ 22 ft² / 80 lb bag |
| Brown coat (base) | 3⁄8 in | ≈ 22 ft² / 80 lb bag |
| Finish coat | 1⁄8 in | ≈ 70 ft² / 80 lb bag |
The three coats and total thickness
Over wood or steel framing, a 3-coat system is applied on metal lath and a weather-resistive barrier, building up to a nominal 7⁄8 in total per ASTM C926 and the SMA guide spec. Over solid masonry like a concrete block wall, the scratch coat can be applied directly and a 2-coat system is common.
| Coat | Role | Thickness | Cure |
|---|---|---|---|
| Scratch | Bonds to the metal lath, scored to key the next coat | 3⁄8 in | 24–48 hr moist |
| Brown | Levels and trues the wall to a flat plane | 3⁄8 in | 7 days moist |
| Finish | Color and texture (float, dash, lace, etc.) | 1⁄8 in | Per product |
The base coats are a portland cement, lime, and sand plaster — the same cement-based family as the material in the concrete calculator, but mixed lean and applied thin. The finish coat carries the color and texture and is usually bought as a separate bagged product.
Notes and assumptions
Coverage figures are typical manufacturer values at the nominal coat thickness; real yield swings with substrate roughness, lath depth, how hard the scratch coat is keyed, and finish texture. Heavy dash or thick float finishes use more. Treat the bag count as an ordering estimate, round up, and keep a spare bag.
A 3-coat system over framing also needs metal lath, corner aid, casing bead, and a weather-resistive barrier, which this take-off does not size beyond the lath sheet count. Moist curing and the wait between coats — at least 24–48 hours after the scratch and about seven days after the brown — are what make the wall crack-resistant, so plan the schedule, not just the materials.