How it works
The calculator finds the area, multiplies it by the thickness of the base coats and the finish coat, and divides each volume by what one bag covers.
Area = Length × Height − Σ (Width × Height × Count of openings)
Base coat volume = Area × (Scratch + Brown) × (1 + Extra ÷ 100)
Finish coat volume = Area × Finish × (1 + Extra ÷ 100)
Bags = ⌈ Volume ÷ (Coverage per bag × Thickness for that coverage) ⌉
⌈ ⌉ means rounding up to the next whole bag. With QUIKRETE’s figures, one bag of base coat is 20 sq ft × 3/8 in = 0.625 cu ft of applied stucco, and one bag of finish coat is 70 sq ft × 1/8 in ≈ 0.73 cu ft.
Thicknesses come from ASTM C926 Table 4 or your own figures. This tool estimates material quantity only; lath, weather-resistive barrier, control joints and the coat system come from your plans, the product instructions and local code.
Worked example
Inputs
- Measure by
- Wall length × height
- Wall length
- 40 ft
- Wall height
- 9 ft
- Doors & windows (no stucco) 1
- Width 3 ft, Height 7 ft, Count 1
- Doors & windows (no stucco) 2
- Width 4 ft, Height 3 ft, Count 2
- Coat system
- Three coats over metal lath – 3/8 + 3/8 + 1/8 in
- Base coat coverage per bag
- 20 sq ft
- Thickness for that coverage
- 3/8 in
- Finish coat coverage per bag
- 70 sq ft
- Thickness for that coverage
- 1/8 in
- Extra allowance
- 0 %
Result
- Bags of base coat
- 32
- Bags of finish coat
- 5
- Area to stucco
- 315 sq ft
- Total thickness
- 0.875 in
- Base coat volume
- 19.69 cu ft (0.729 cu yd)
- Finish coat volume
- 3.28 cu ft (0.122 cu yd)
Common mistakes
- Buying one product for every coat. Scratch and brown coats use a base coat mix; the finish coat is a separate product with its own coverage.
- Using the bag yield as coverage at any thickness. Coverage drops in proportion to thickness – a bag that covers 20 sq ft at 3/8 in covers about 10 sq ft at 3/4 in.
- Measuring from the face of the lath. ASTM C926 measures thickness from the back of the metal lath, so the lath sits inside the first coat.
- Forgetting texture. Heavy textures add material beyond the nominal finish coat thickness.
Assumptions and limits
- Area = length × height minus doors and windows, or the area you enter.
- Base coat volume = area × (scratch + brown) thickness; finish coat volume = area × finish thickness; any extra allowance is added to both.
- Bags = volume ÷ (coverage per bag × the thickness that coverage refers to), rounded up, separately for base and finish coat.
- Preset thicknesses are the nominal vertical values of ASTM C926 Table 4, exclusive of texture. The result is a material quantity only.
Frequently asked questions
How thick is three-coat stucco?
ASTM C926 Table 4 lists 3/8 in scratch, 3/8 in brown and 1/8 in finish over metal lath on vertical work, 7/8 in in total. Over masonry or concrete the three coats total 5/8 in. Follow your plans and local code.
How much does a bag of stucco cover?
Check the data sheet. QUIKRETE lists 20–24 sq ft at 3/8 in, 15–18 sq ft at 1/2 in and 10–12 sq ft at 3/4 in for an 80 lb bag of Scratch and Brown Base Coat Stucco, and about 70 sq ft at 1/8 in for an 80 lb bag of Finish Coat Stucco.
How many bags of stucco for 100 square feet?
For three coats over metal lath with QUIKRETE’s figures, the 3/4 in of base coat takes 100 × 3/4 ÷ (20 × 3/8) = 10 bags, and the finish coat 100 ÷ 70 = 1.4, so 2 bags, before any extra.
Can I use metric bag figures?
Yes. Switch to metric and enter the coverage in square meters at the thickness in millimeters, as printed on your product’s data sheet.
Sources
- ASTM C926-11a Standard Specification for Application of Portland Cement-Based Plaster, Table 4 — ASTM International (copy published by the Florida Building Commission). Table 4 nominal thickness, vertical: three-coat over metal plaster base 3/8 + 3/8 + 1/8 = 7/8 in (9.5 + 9.5 + 3 = 22 mm); three-coat over unit masonry or concrete 1/4 + 1/4 + 1/8 = 5/8 in; two-coat over unit masonry 3/8 + 1/8 = 1/2 in; two-coat over cast-in-place or precast concrete 1/4 + 1/8 = 3/8 in.
- QUIKRETE Scratch and Brown Base Coat Stucco (No. 1139) Product Data Sheet, rev. October 2021 — The QUIKRETE Companies. 80 lb bag "will yield approximately 0.75 ft3 (21 L)"; covers "3/8 inch (9.5 mm) 20 ft2 to 24 ft2 (1.8 m2 to 2.2 m2)", 1/2 in 15–18 sq ft, 3/4 in 10–12 sq ft (default 20 sq ft at 3/8 in, the low end).
- QUIKRETE Finish Coat Stucco (No. 1201) Product Data Sheet — The QUIKRETE Companies. "Each 80 lb (36 kg) bag will yield approximately 0.75 ft3 (20 L) of material. Coverage will be approximately 70 ft2 (6.5 m2) at 1/8" (3.2 mm)"; minimum 1/8 in finish coat.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 6, 2026