How much cement is needed for 100 m² of 12 mm plaster?

About 6.5 bags at 1:6 before wastage. Wet volume 100 × 0.012 = 1.2 m³, dry 1.2 × 1.33 = 1.6 m³, cement share one seventh = 0.228 m³, divided by 0.0347 m³ per bag.

Which plaster ratio should I use?

1:6 is common for internal walls, 1:4 for external walls and ceilings. Your engineer may specify otherwise.

Why is the dry volume 1.33 times the wet volume?

Dry cement and sand have air gaps that fill when water is added, so you need about a third more dry material than the wet mortar volume.

Plaster calculator

Work out cement and sand for wall plaster or a floor tiling bed before you order.

Formula and assumptions

Wet mortar = area × thickness. Dry volume = wet × 1.33, then each material takes its share of the mix ratio, and cement volume ÷ 0.0347 m³ gives 50 kg bags. Wall plaster is commonly 12 mm inside and 15 to 20 mm outside, in 1:4 to 1:6. Floor tiling bed is typically 25 to 50 mm, often 1:4.

Plaster area (m²)

Thickness

Mix ratio (cement:sand)

Wastage (%)

Wet mortar: 1.20 m³
Cement: 6.9 bags (50 kg)
Sand: 1.44 m³ (50.7 cu ft)

Estimate only. Wastage is added (5% by default), and uneven walls or slabs can need more. Confirm the mix with your engineer or mason.

Need materials?

We stock cement, bricks, blocks and more at Kanth Road, Amroha. See our cement.

FAQ

How much cement is needed for 100 m² of 12 mm plaster?: About 6.5 bags at 1:6 before wastage. Wet volume 100 × 0.012 = 1.2 m³, dry 1.2 × 1.33 = 1.6 m³, cement share one seventh = 0.228 m³, divided by 0.0347 m³ per bag.
Which plaster ratio should I use?: 1:6 is common for internal walls, 1:4 for external walls and ceilings. Your engineer may specify otherwise.
Why is the dry volume 1.33 times the wet volume?: Dry cement and sand have air gaps that fill when water is added, so you need about a third more dry material than the wet mortar volume.

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