Stucco Calculator: Bags of Base and Finish Coat

How do you calculate how much stucco you need?

Multiply the wall area by the coat thickness to get a volume, then divide by the volume one bag makes. Do it separately for the base coats and the finish coat, because they are different products with different yields.

Net area (ft²) = wall area − openings
Volume (ft³) = net area × thickness (in) ÷ 12 × (1 + waste %)
Bags = volume ÷ yield per bag, rounded up

Yields used. QUIKRETE’s Scratch and Brown Base Coat Stucco data sheet says an 80 lb (36.2 kg) bag yields about 0.75 ft³ (21 L) at the recommended consistency. Its coverage figures follow from that: 0.75 ÷ (3/8 ÷ 12) = 24 ft² at 3/8 in, the top of the sheet’s 20–24 ft² range. QUIKRETE’s Stucco Selector Guide gives Finish Coat Stucco 70 ft² per 80 lb bag at 1/8 in, which is about 0.73 ft³. The sheet notes coverages “are approximate and vary with thickness, waste, etc.”, so keep the extra allowance.

Measure each wall as length × height, add gable triangles (½ × base × height), and subtract windows and doors. Returns around openings and corners still take material, so do not subtract small openings.

How much does a bag of stucco cover? (by thickness)

At 3/8 in, an 80 lb bag of base coat covers about 24 ft²; each extra 1/8 in of thickness cuts the coverage sharply. The table uses the 0.75 ft³ yield, so the coverage is at the top of QUIKRETE’s printed ranges.

The finish coat is a separate product with its own yield: about 70 ft² (6.5 m²) per 80 lb bag at 1/8 in, or roughly 1.4 bags per 100 ft². Textured finishes applied thicker than 1/8 in use more; scale the finish line by thickness.

How many bags of stucco for common wall areas?

The table gives 80 lb bags with 10% extra. The 3-coat column is 3/4 in of scratch and brown coat; the 2-coat column is a single 3/8 in base coat, as used over masonry or concrete. Both need the finish coat on top.

What is the difference between 3-coat, 2-coat and one-coat stucco?

The number of coats depends on what you are covering. QUIKRETE’s selector guide describes three routes, each with a 3/8 in minimum for the base layer:

• 3-coat over lath. A scratch coat is pressed through metal lath and scored, then a brown coat levels the wall, then the finish coat adds colour and texture. With QUIKRETE’s minimums that is 3/8 + 3/8 + 1/8 = 7/8 in in total.
• 2-coat over masonry or concrete. A solid base like concrete block or cast concrete needs no scratch coat to key into lath, so one base coat (minimum 3/8 in) and a finish coat go on. Keep the block or concrete damp before applying, as the data sheet advises in hot weather.
• One-coat systems. Proprietary fiber-reinforced products (QUIKRETE lists one under IAPMO evaluation report ER-455) apply in a single base layer of at least 3/8 in, then a finish. Their coverage is the same 20–24 ft² per bag at 3/8 in.

The calculator’s presets follow these minimums. If your plans call for a thicker coat, pick Custom and type the total base thickness. ASTM C926 sets requirements for the application of portland cement-based plaster, including lath and control joints; your local building code and the lath manufacturer decide the details.

Stucco calculator in metric

The formula is the same in metres: volume (m³) = area (m²) × thickness (m), then divide by the bag yield of 0.021 m³ (21 L) per 80 lb (36.2 kg) bag.

How do you mix and cure stucco so the bags go the right distance?

Mix only what you can use in an hour, apply in the right weather, and keep it moist. These points come from QUIKRETE’s Scratch and Brown data sheet:

1. Water first. About 5 1/2 quarts (5.2 L) per 80 lb bag, then the powder, mixed 3 to 5 minutes in a paddle mortar mixer or by hand.
2. One-hour batches. Prepare only what you can apply within 1 hour and keep retempering to a minimum. Stucco thrown out at the end of the day is part of the waste allowance.
3. Weather window. No application when the forecast is above 100 °F (38 °C) or below 40 °F (4 °C) within 24 hours unless you follow hot- or cold-weather precautions (ACI 305R and 306R). Protect from rain, snow and freezing for 48 hours.
4. Moist cure. Once the stucco reaches final set, mist it with a fine spray per ASTM C926; in hot, dry or windy weather, spray more often or shade the wall.
5. Lath and paper. Install wire lath and building paper to ASTM C926 or your local code before the scratch coat.

Common stucco estimating mistakes

• Using finish coat coverage for the base. 70 ft² per bag is for a 1/8 in finish. The base coats take about six times as much per square foot.
• Ignoring uneven walls. Hollows in block or framing take extra brown coat to level. If the wall is visibly out of plane, add more than 10%.
• Mixing too much at once. Material that stiffens before you use it cannot be retempered indefinitely.
• Forgetting the gables and soffits. Measure every surface that gets stucco, not only the main walls.
• Treating coverage as exact. QUIKRETE prints a range; the calculator uses the top of it, so the waste allowance matters.

All results are ordering estimates. The bag’s own data sheet, your plans and local code take priority. This page names QUIKRETE because its data sheets are public; other brands publish their own yields, which you can enter in the calculator.