How much cement and sand for plastering?

Multiply the wall area by the plaster thickness to get wet volume, scale by 1.33 for dry volume, then split by the cement:sand ratio. For a 1:6 plaster at 12 mm, roughly 0.09 bags of cement and 0.5 cubic feet of sand are needed per square metre.

What thickness should plaster be?

Internal walls are usually plastered 12 mm thick, external walls 15 to 20 mm, and ceilings around 6 mm.

What is the best ratio for plaster?

A 1:4 to 1:6 cement-to-sand ratio is common; 1:4 for external and stronger work, 1:6 for internal walls.

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Materials

Plaster Calculator

Enter the wall area and plaster thickness to get the cement and sand you need. Defaults to a 12 mm internal plaster at 1:6; change the thickness and ratio for external walls or ceilings.

All materials Concrete Cement Sand Aggregate Brick Plaster Tile Flooring Paint Roofing Steel

Area & mix

Area measured in

Plaster area sq ft

Thickness mm

Cement : sand ratio

Wastage 15%

Cement required—

Sand—

Wet mortar volume—

Add rates for a cost

Cement ₹/bag

₹

Sand ₹/cft

₹

How it's calculated

Wet plaster volume is area × thickness. Plastering adds extra mortar for uneven surfaces and wastage, so a higher wastage allowance (10–20%) is normal. The wet volume is scaled by 1.33 to dry volume and split by your cement:sand ratio.

Wet volume = area × thickness → ×1.33 dry → split by ratio → cement ÷ 0.0347 = bags.

Just built the wall? Get the bricks first with the brick calculator, then paint it with the paint calculator.

Frequently asked questions

What thickness for internal walls?

12 mm is standard internally; 15–20 mm externally; ~6 mm for ceilings.

Why such high wastage on plaster?

Uneven masonry, droppings and finishing losses mean plaster commonly needs 10–20% extra mortar.

Which ratio?

1:6 internal, 1:4 external or where a stronger, denser finish is wanted.

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