Stucco calculator

Common questions

How many bags of stucco do I need?

It depends on how many coats, and that is the question most calculators skip. Five hundred square feet in a three coat system at 3/8 inch a coat takes 50 bags of base coat and 8 of finish — 58 in total. The same wall in a two coat system takes 25 plus 8. The difference is not the finish; it is that a three coat job applies the base twice.

How much does a bag of stucco cover?

An 80 lb bag of QUIKRETE Scratch and Brown Base Coat covers 20 to 24 square feet at 3/8 inch, 15 to 18 at 1/2 inch and 10 to 12 at 3/4 inch. An 80 lb bag of Finish Coat covers about 70 square feet at 1/8 inch. Those are wildly different numbers because they are different materials doing different jobs, and adding them into one "stucco covers X" figure — as most pages do — makes both wrong.

What is the difference between a two coat and a three coat system?

Three coat is the traditional build-up over metal lath: a scratch coat, a brown coat and a finish coat, with the first two being the same base material. Two coat puts the base on once, and it is normal over solid masonry or concrete where there is no lath to embed. What your wall needs is set by ASTM C926 for your substrate, not by preference — and it changes the material order by roughly a factor of two, which is why it is the first thing this tool asks.

How thick should each coat be?

The base coat products here are published at a minimum 3/8 inch, and the calculator only offers the thicknesses the manufacturer published a coverage for. The actual thicknesses your assembly needs come from ASTM C926 and vary with the substrate, the lath and whether the wall is vertical or a soffit. Take them off your specification. Guessing thicker costs money by the pallet; guessing thinner fails inspection.

Do I need to add for waste?

Yes, and the published figures already say they are approximate — "all coverages are approximate and vary with thickness, waste, etc." Stucco is mixed in batches, and what is left in the hawk and the mixer at the end of a batch does not go into the next one. A five per cent allowance is a starting point rather than a published number, which is why it is a field you can change rather than something baked into the answer.

Does the finish texture change how much I need?

Materially. QUIKRETE's own data sheet says coverage "will vary with texture" — a heavy dash or a coarse sand finish carries far more material than a smooth float, at the same nominal thickness. The Color and Texture Finish Coat is published at two thicknesses precisely because of this: 100 to 103 square feet a bag at 1/16 inch and 24 to 27 at 1/4. Pick the thickness that matches the texture you are actually applying.

What about the lath, the paper and the beads?

Not counted here, and on a re-render they are usually most of the material list. Weather-resistive barrier, metal lath, weep screed, casing bead, corner bead, control joints and the fasteners for all of it are separate orders governed by your assembly. This tool answers the question it can answer exactly — how many bags of mixed material go on the wall — and says plainly what it is leaving out.

Should I deduct windows and doors?

Deduct the openings before you enter the area, but do not deduct the returns. The reveals around a window are stucco too, and on a wall with a lot of openings the returns can put back a fair share of what the openings took out. If you are working from a rough wall area with no deductions, you are carrying the openings as waste — which on a wall that is mostly glass is a lot of bags.