How to Calculate Plastering Quantity

Plastering is the process of applying a thin layer of cement mortar to walls and ceilings to create a smooth, durable surface. Calculating the correct quantity of cement and sand for plastering is important for material procurement and cost control.

The first step is to calculate the plastering area. Measure the length and height of each wall and multiply them to get the area. Subtract the area of openings such as doors, windows, and ventilators. The total plastering area is the sum of all wall and ceiling areas.

The standard plastering thickness for internal walls is 12 mm, and for external walls it is 15 to 20 mm. The mix ratio for internal plastering is typically 1:4 (one part cement to four parts sand), and for external plastering it is 1:5 or 1:6.

To calculate the material quantity, first determine the wet volume of mortar by multiplying the plastering area by the thickness. Then multiply by 1.3 to get the dry volume (to account for voids and bulking of sand). For a 1:4 mix, cement is 1/5 of the dry volume and sand is 4/5 of the dry volume.

For example, for 100 square metres of internal plastering with 12 mm thickness, the wet volume is 100 x 0.012 = 1.2 cubic metres. The dry volume is 1.2 x 1.3 = 1.56 cubic metres. For a 1:4 mix, cement volume is 0.312 cubic metres (approximately 9 bags of 50 kg) and sand volume is 1.248 cubic metres.

Use our plastering calculator for quick and accurate calculations for your specific wall dimensions and mix ratios.