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.