How much stucco a wall needs — coat by coat. Volumes for scratch, brown and finish coats from your wall area and thicknesses, then either bags from your product’s yield or sand and cement at your mix ratio. The same math covers render and cement plaster.
Units
System
3/8″ is common practice over lath.
3/8″ common; brings the base to depth.
1/8″ typical for a cement finish.
Droppage off the trowel is real — 10–15% is normal.
Material
From your bag’s label — base-coat bags commonly yield roughly 0.6–0.9 ft³. Coverage depends on thickness, not just the bag.
3:1 sand to cement is the textbook plastering mix; some coats use 4:1.
Dry, loose materials compact when mixed wet; ~1.3 is standard.
Geometry × thickness only. Coat thicknesses shown are common practice — your system, substrate and local requirements govern. Bag yields vary by product; read your bag. Field-mix splits are computed from the ratio you enter.
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Bulk sand or mortar instead?
Once you know the sand tonnage, order it with the Sand Calculator (masonry sand preset). Laying brick rather than coating it? The Brick & Mortar Calculator figures units and mortar together.
How much stucco do I need? Coverage comes from thickness
Stucco quantity is pure geometry: wall area times coat thickness gives the volume of each coat, and everything else — bags, sand, cement — follows from that volume. That’s why “coverage per bag” questions have no single answer: a bag that does 25 ft² at 3/8″ does 75 ft² at 1/8″.
coat volumeft³ = net wall areaft² × (thicknessin ÷ 12) bags = total volume ÷ your bag’s yieldft³ field mix: dry volume = wet × 1.3; cement = dry ÷ (1 + ratio); sand = dry − cement
3-coat stucco: scratch, brown and finish
The traditional hard-coat system over lath is three layers: a 3/8″ scratch coat raked horizontally for key, a 3/8″ brown coat that levels the wall, and a 1/8″ finish coat for texture — about 7/8″ total, the depth set by the grounds and screeds. Those thicknesses are common practice, and the fields above are editable if your system differs (some crews run the scratch thinner and the brown thicker to the same total).
2-coat over masonry
On concrete or block, the lath and scratch stage isn’t needed for key, so a 2-coat system — roughly a 3/8″ base plus a 1/8″ finish, about 1/2″ total — is typical. Switch the system tab and the brown coat drops out; the math is otherwise identical.
Render calculator — the same math, UK phrasing
What North America calls stucco, the UK and much of the world calls render: a sand-cement coating on external masonry, usually two coats around 10–15 mm total. Switch to metric, enter the wall in metres and the coats in millimetres, and this page works as a render calculator directly — volumes come out in m³ with the sand in tonnes.
Plaster calculator and the cement-and-sand ratio for plastering
Internal cement plastering runs on the same volume math. The classic cement and sand ratio for plastering is 1:3 (one cement to three sand) for base coats, with leaner 1:4 mixes on less demanding coats. In field-mix mode the calculator multiplies the wet volume by a 1.3 dry-volume factor (loose dry materials compact when mixed), splits the dry volume by your ratio, and reports cement in bags — counting a 94 lb cement bag as one cubic foot — and sand in tons and yards.
Scratch coat calculator
Need just the first coat — for a stone veneer scratch coat or a repair? Set the brown and finish thicknesses to zero and the result is the scratch coat alone: area × 3/8″ ÷ 12, plus waste. The per-coat breakdown in the results always shows each coat separately, so you can also stage purchases coat by coat.
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Frequently asked questions
How many square feet does a bag of stucco cover?
It depends entirely on thickness: coverage ft² = bag yield ft³ ÷ (thickness″ ÷ 12). A 0.7 ft³ bag covers ~22 ft² at 3/8″ but ~67 ft² at 1/8″. Enter your bag’s yield from its label and the calculator does the rest.
How many coats of stucco do I need?
Over lath (wood-framed walls): the traditional 3 coats — scratch, brown, finish, ~7/8″ total. Directly over masonry or concrete: 2 coats (~1/2″) is typical. One-coat proprietary systems exist but follow their own product instructions.
What is the mix ratio for stucco?
Field-mixed base coats are commonly around 3 parts sand to 1 part cement (often with lime added for workability); finish and some brown coats run leaner at 4:1. The ratio field is editable, and the split is computed from whatever you enter.
How much sand and cement for 100 ft² of stucco?
At 7/8″ total (3-coat): 100 × 0.875/12 = 7.3 ft³ wet ≈ 9.5 ft³ dry with the 1.3 factor. At 3:1 that’s ~2.4 ft³ of cement (≈ 2–3 bags) and ~7.1 ft³ of sand (~0.36 tons) — before waste. The calculator shows it live for your real numbers.
Does this work for render and plaster?
Yes — render and cement plaster are the same material family with the same volume math. Use metric units and millimetre coat thicknesses (render is commonly ~10–15 mm in two coats), and field-mix mode for the sand-cement split.