Calculate the sand and cement needed for wall or ceiling plastering, based on the area, plaster thickness, and mix ratio.
How to Use the Sand Calculator
Enter the "Plaster Area (m²)" of the wall or ceiling.
Enter the "Plaster Thickness (mm)" - typically 12-15mm for internal walls.
Enter your "Mix Ratio" for Cement and Sand (e.g. 1:6 for internal plaster, 1:4 for external plaster).
Click "Calculate" to see the sand and cement required.
How Sand and Cement for Plaster Are Calculated
Wet volume of plaster = Area × Thickness (thickness converted from mm to m). This is the volume of finished plaster on the wall.
Dry volume = Wet volume × 1.33. Dry sand and cement shrink when water is added and some mortar is lost in joints and on the floor, so you need about a third more dry material than the finished volume.
The dry volume is shared out by the mix ratio. In a 1:6 mix, cement is 1/7 of the dry volume and sand is 6/7.
Plastering 100 m² of internal brick wall 12 mm thick in 1:6: wet volume = 100 × 0.012 = 1.2 m³. Dry volume = 1.2 × 1.33 = 1.596 m³. Cement = 1.596 ÷ 7 = 0.228 m³, which is 0.228 × 1,440 = 328 kg or about 6.6 bags, so the tool shows 7 bags. Sand = 1.596 × 6 ÷ 7 = 1.368 m³, about 2,189 kg or roughly 48 cubic feet.
The same 100 m² at 12 mm with different mix ratios:
Mix (cement:sand)
Cement bags
Sand (m³)
Sand (cft)
1:3
12
1.197
42.3
1:4
10
1.277
45.1
1:5
8
1.330
47.0
1:6
7
1.368
48.3
Typical Plaster Thickness and Mix
These are common practices on Indian building sites. Your architect or contractor's specification takes priority.
Surface
Usual thickness
Usual mix
Ceiling (RCC slab)
6 mm
1:3 or 1:4
Internal wall, smooth side of brickwork
12 mm
1:6
Internal wall, rough or uneven side
15 mm
1:5 or 1:6
External wall, applied in two coats
18–20 mm
1:4
Each extra millimetre adds roughly 8% to the material for a 12 mm job, so an uneven wall that needs 18 mm in patches uses noticeably more sand and cement than the drawing suggests. Measure a few spots before you estimate.
Buying Sand in India
Units differ by region. Sand is sold by the cubic foot, by the tonne, by the truck or tractor load, or by the brass. One brass is 100 cubic feet, which is about 2.83 m³. To convert this tool's result, multiply cubic metres by 35.3 to get cubic feet.
Use fine sand for plaster. Plastering sand, including manufactured P-sand, is finer than the sand used for concrete or brickwork. Coarse sand gives a rough finish and more surface cracks.
Damp sand bulks up. Moist sand can occupy noticeably more volume than the same sand when dry, so a load measured by volume when wet contains less sand than it appears. Buying by weight avoids this.
Leave the walls wet before plastering and cure the plaster with water for about a week afterwards. Poor curing, not the mix ratio, is the most common cause of hairline cracks.
Frequently Asked Questions
Plaster mortar (cement + sand only, no coarse aggregate) typically uses a dry volume factor of around 1.33, compared to 1.54 for concrete mixes that include aggregate - both account for voids and bulking, but the exact factor depends on the mix composition.
A 1:6 (cement:sand) ratio is common for internal wall plastering, while a richer 1:4 ratio is often used for external plastering, which is more exposed to weather.
This tool is tuned for plastering (cement + sand only). For concrete mixes that also include coarse aggregate, use the Cement Calculator instead, which handles the three-part cement:sand:aggregate ratio.
With this tool's assumptions, one 50 kg bag covers about 15 m² of 12 mm plaster in a 1:6 mix, or about 11 m² in a 1:4 mix. Thicker plaster or a richer mix covers less.
Multiply the cubic metre figure by 35.3 to get cubic feet. Divide the cubic feet by 100 to get brass. For example, 1.368 m³ is about 48 cft, or roughly half a brass.