Wall Plaster Quantity Calculator

Plaster cement sand quantity calculator per square foot for 12mm and 15mm wall plaster. Use the free Wall Plaster Quantity Calculator below — enter your values and get instant results, right in your browser. Dry mortar per sq ft = 0.001483 m³ (12 mm) or 0.001854 m³ (15 mm). Cement bags = area × dry volume × 1/(1+ratio) × 28.8. Sand (cu ft) = area × dry volume × ratio/(1+ratio) × 35.31.

How to use the Wall Plaster Quantity Calculator

Plaster looks simple — a thin coat of cement and sand — but its material adds up fast across a whole house, and guessing wrong means the plasterer stands idle while you rush to the dealer. This plaster cement sand quantity calculator per square foot handles the two standard thicknesses: 12 mm for interior walls and 15 mm for exterior walls that need extra weather protection. Pick your mortar ratio, enter the wall area, and get the exact cement bags and sand volume before the work starts.

  1. Measure the wall area in square feet and enter it in the Wall area field.
  2. Select the plaster thickness — 12 mm for interior walls, 15 mm for exterior.
  3. Select the mortar ratio — 1:6 for interior, 1:4 for exterior or damp areas.
  4. Click Calculate to see the cement bags and sand required.

Formula

Dry mortar per sq ft = 0.001483 m³ (12 mm) or 0.001854 m³ (15 mm). Cement bags = area × dry volume × 1/(1+ratio) × 28.8. Sand (cu ft) = area × dry volume × ratio/(1+ratio) × 35.31.

Worked example

Plastering 200 sq ft of interior wall at 12 mm with 1:6 mortar: dry mortar = 0.297 cubic metres, cement = 0.297 × 1/7 × 28.8 = 1.22 bags, sand = 0.297 × 6/7 × 35.31 = 9.0 cubic feet. Buy 2 bags of cement and half a trolley of sand, and the plasterer can finish the room without a second market trip.

Frequently asked questions

About 0.61 bags of cement and 4.5 cubic feet of sand for 12 mm plaster with 1:6 mortar.

Exterior walls get 15 mm plaster with 1:4 mortar to resist rain and weather; interior walls need only 12 mm with 1:6 mortar.

Yes — measure the full wall and subtract door and window openings for an accurate material estimate.

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