How to Use the Plaster/Stucco Mortar Calculator
Cement plaster and stucco finishes are applied in one or more coats over lath or masonry to create a durable exterior or interior wall surface. Getting the material quantity right before mixing matters because plaster sets up quickly once mixed. This calculator takes your plaster area, coat thickness, and the mix density to give you the required volume, weight, and number of bags.
Cement-based plaster mixes typically run 110-130 lb per cubic foot depending on the sand-to-cement ratio and how well the mix is compacted; this calculator defaults to 120 lb/cu ft as a representative value. For the most accurate order quantity, check the coverage or density figure listed on your specific product's bag or technical data sheet.
A traditional three-coat stucco system (scratch, brown, and finish coats) typically totals about 7/8 in in thickness, while a single skim coat is much thinner. Uneven substrates need more material in the low spots, so base your thickness entry on the average across the wall and order a little extra to avoid running short mid-application.
Frequently Asked Questions
Cement-based plaster and stucco mixes typically have a bulk density of around 110-130 lb per cubic foot depending on mix ratio and compaction. This calculator uses 120 lb/cu ft as a representative default, but you should switch to the value on your specific product's data sheet for a more precise result.
A typical scratch and brown coat combination runs about 5/8 to 7/8 in total, while a single finish coat is much thinner. If the substrate is uneven, use the average thickness across the area and order extra material to cover the higher spots.