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.

Quick answer: To estimate stucco, find the net wall area, add waste, and divide by the coverage of each coat: an 80 lb bag of base coat covers about 27 sq ft at 3/8 in and an 80 lb bag of finish about 70 sq ft at 1/8 in. A 40 x 9 ft wall with 40 sq ft of openings (320 sq ft, or 352 with 10% waste) needs 27 bags of base coat for the scratch and brown coats, 6 bags of finish and 20 sheets of lath.

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
80 lb bags of finish coat: 6 bags; 1/8 in finish at about 70 sq ft per bag, including 10% waste
Metal lath sheets: 20 sheets; 27 in x 96 in sheets, 18 sq ft each, including 10% for laps and cuts
Wall area: 320 sq ft; 352 sq ft with waste; scratch and brown coats plus finish, 7/8 in total thickness
Grade D building paper: 2 rolls; Two layers over wood sheathing at 500 sq ft per roll, including 10% for laps

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 ft

Worked 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

Stucco materials by wall area (10% waste, 10% lath overlap)
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 layers of building paper, metal lath, then the base coats and a finish coat. 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% waste there. Order all the bags for a wall at once so the color and texture of the finish match from one mixer load to the next.

Over concrete block or poured concrete that is clean and unpainted, stucco can bond directly and the paper and lath are usually skipped. Painted or smooth masonry needs a bonding agent or lath.

Three-coat vs one-coat systems

The traditional three-coat system builds 3/4 in of cement base in two lifts before the finish, which makes it the most crack-resistant and the thickest barrier against impact and weather. It also takes the longest: about 48 hours of moist curing after the scratch coat and a week after the brown coat before the finish.

One-coat stucco is a fiber-reinforced base applied about 1/2 in thick in a single pass over lath, usually with a layer of foam insulation board behind it. It cuts labor and cure time but is thinner, so it needs good control joints and a careful weather barrier. 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.

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 requires a water-resistive barrier equal to two 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.

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 many sheets of metal lath do I need?

Each 27 x 96 in sheet covers 18 sq ft. Divide the wall area by 18 and add 10% for laps and cuts: a 320 sq ft wall needs 20 sheets.

Do I need building paper behind stucco?

Yes, over wood framing and sheathing. Code calls for two layers of Grade D paper or an equivalent barrier under the lath. Stucco applied directly to clean concrete or block does not need paper.

Sources and references

Next steps for this project

The usual order for a paint & walls project. See all paint & walls calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.