Stucco Calculator
Estimate bags of base coat and finish coat stucco, metal lath sheets and building paper for a wall, for a traditional three-coat or a one-coat stucco system.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- 80 lb bags of base coat
- 27 bags
- Scratch and brown coats of 3/8 in each, about 13.5 sq ft per bag for both, including 10% waste. 33 bags total is 2,640 lb, a pallet delivery
- 80 lb bags of finish coat
- 6 bags
- 1/8 in finish at about 70 sq ft per bag, including 10% waste. Buy all from one lot number
- Metal lath sheets
- 20 sheets
- 27 in x 96 in sheets, 18 sq ft each, including 10% for laps and cuts. Self-furring, fastened into framing 7 in on center (ASTM C1063)
- Wall area
- 320 sq ft
- 352 sq ft with waste; scratch and brown coats plus finish, 7/8 in total thickness. ASTM C1063 limits panels to 144 sq ft and 18 ft in any direction, so plan at least 2 control joints plus one at each floor line
- Grade D building paper
- 2 rolls
- Two independent layers over wood sheathing (IRC R703.7.3) at 500 sq ft per roll, including 10% for laps, lapped over the weep screed flange
Stucco formula
Wall area = Length x Height - openings; Order area = Wall area x (1 + waste %)
Base coat bags = Order area / 13.5 sq ft (3-coat: two 3/8 in coats at 27 sq ft per bag each) or / 20 sq ft (one-coat 1/2 in base)
Finish coat bags = Order area / 70 sq ft per 80 lb bag at 1/8 in
Lath sheets = Wall area x (1 + lap %) / 18 sq ft; Paper rolls = Wall area x (1 + lap %) x 2 layers / 500 sq ftWorked example
A 30 x 8 ft garage wall with 24 sq ft of openings, three-coat system: 30 x 8 - 24 = 216 sq ft, or 237.6 sq ft with 10% waste. Base coat: 237.6 / 13.5 = 17.6, so 18 bags. Finish coat: 237.6 / 70 = 3.4, so 4 bags. Lath with 10% for laps: 237.6 / 18 = 13.2, so 14 sheets. Paper: 237.6 x 2 layers / 500 = 0.95, so 1 roll.
The same wall with a one-coat system needs 237.6 / 20 = 11.9, so 12 bags of base plus the same 4 bags of finish.
Quick reference
| Wall area | 3-coat base bags | 1-coat base bags | Finish bags | Lath sheets |
|---|---|---|---|---|
| 100 sq ft | 9 | 6 | 2 | 7 |
| 200 sq ft | 17 | 11 | 4 | 13 |
| 300 sq ft | 25 | 17 | 5 | 19 |
| 500 sq ft | 41 | 28 | 8 | 31 |
| 800 sq ft | 66 | 44 | 13 | 49 |
| 1,000 sq ft | 82 | 55 | 16 | 62 |
How to estimate stucco
Stucco over a framed wall is a sandwich. Two independent layers of Grade D paper or equivalent (IRC R703.7.3), then self-furring metal lath fastened to the framing 7 in on center, then the base coats and finish. Measure the net wall area, add 10% for waste, and divide by the coverage on the bag; coverage drops on rough masonry or where the lath is furred out, so lean toward 15% there. Buy every bag of finish from one lot number. Run a full wall at a time and stop only at corners or control joints, or the cold joint shows.
The wall also needs a weep screed at the bottom, 4 in above soil or 2 in above paving (R703.7.2.1), with the paper lapped over its flange. Add casing bead at every opening and control joints. ASTM C1063 limits each panel to 144 sq ft and 18 ft in any direction, with a joint at every floor line. A 40 x 9 ft wall gets two vertical joints. Over clean, unpainted block or poured concrete the base coat bonds directly and lath is skipped; painted or form-oiled concrete needs a bonding agent or lath.
Three-coat vs one-coat systems
Three-coat is the prescriptive system in IRC R703.7: 3/8 in scratch, 3/8 in brown and a 1/8 in finish, 7/8 in total over lath. It is the most crack- and impact-resistant wall and takes the longest. Each base coat is kept moist 48 hours (ASTM C926) and the brown coat cures 7 days before the finish, so a wall is two weeks of site time. Nothing goes on below 40 F or onto a frozen or sun-baked wall; fog the brown coat in hot wind.
One-coat stucco is a fiber-reinforced base applied about 1/2 in thick in a single pass over lath, usually over foam board. It is proprietary, so the inspector wants the ICC-ES evaluation report and the crew follows it for lath and fasteners. Both systems can take a cement finish from the bag or an acrylic finish from a pail; acrylic coverage depends heavily on texture, so check the pail rather than this calculator. New cement finish cures 28 days before paint or a fog coat.
What this calculator leaves out
Weep screed, casing bead, corner aid and control joints, all sold in 10 ft sticks by the linear foot. Lath fasteners, about 50 per sheet of 1-1/2 in galvanized roofing nails or 7/8 in crown staples, self-adhered flashing at windows, and a bonding agent on masonry. Mixer rental, typically $75 to $150 a day, scaffold, and integral color or acrylic finish. The default wall's 33 bags weigh 2,640 lb, a pallet delivery.
Mistakes that cost money
- One layer of housewrap under lath fails inspection; IRC R703.7.3 calls for two independent layers equal to Grade D paper over wood sheathing.
- Running stucco to grade with no weep screed traps water in the wall; set it 4 in above soil or 2 in above paving (R703.7.2.1).
- Skipping control joints guarantees cracks; ASTM C1063 limits panels to 144 sq ft and 18 ft in any direction, with joints at floor lines.
- Finishing over a brown coat under 7 days old, or a scratch coat not kept wet 48 hours, telegraphs shrinkage cracks (ASTM C926).
- Lath nailed flat to the sheathing leaves no key behind it and the base coat delaminates; use self-furring lath fastened to framing 7 in OC.
- Stopping a finish coat mid-wall leaves a cold joint that shows in every light; mix one lot and stop only at corners or control joints.
Key facts
- Traditional three-coat stucco is 7/8 in thick: a 3/8 in scratch coat, a 3/8 in brown coat and a 1/8 in finish coat, per ASTM C926.
- An 80 lb bag of base coat stucco covers about 27 sq ft at 3/8 in, so the scratch and brown coats together use one bag per 13.5 sq ft.
- Standard expanded metal lath weighs 2.5 lb per square yard and comes in 27 x 96 in sheets that cover 18 sq ft each.
- The IRC (R703.7.3) requires a water-resistive barrier equal to two independent layers of Grade D paper behind stucco over wood-based sheathing.
- Each base coat should be kept moist for at least 48 hours, and the brown coat should cure about 7 days before the finish coat goes on (ASTM C926).
Frequently asked questions
How many bags of stucco do I need per 100 square feet?
For a three-coat system with 10% waste, about 9 bags of 80 lb base coat for the scratch and brown coats and 2 bags of finish per 100 sq ft. A one-coat system needs about 6 bags of base per 100 sq ft.
How much does an 80 lb bag of stucco cover?
About 27 sq ft at 3/8 in thick for base coat, or 20 sq ft at the 1/2 in thickness of a one-coat base. An 80 lb bag of finish coat covers about 70 sq ft at 1/8 in.
How long before I can paint new stucco?
A cement finish coat cures about 28 days before paint; sooner and the alkalinity burns through it. Use a fog coat or an acrylic or elastomeric masonry paint. Between coats, keep scratch and brown moist 48 hours each and give the brown coat 7 days before the finish (ASTM C926).
Do I need building paper behind stucco?
Yes, over wood framing and sheathing. IRC R703.7.3 calls for two independent layers equal to Grade D paper under the lath, lapped shingle fashion over the weep screed flange. Stucco applied directly to clean concrete or block does not need paper.
Sources and references
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.