Plastering cement and sand calculator
Calculate plastering materials
Enter the area (or length × height), pick a thickness and ratio — results update as you type.
Materials required
Wet volume: 0
- Cement (bags)0
- Cement (weight)0
- Sand (volume)0
- Sand (weight)0
- Estimated material cost₹0
Sample figures shown for illustration — pending verification against real Tirupati market rates before publishing as fact.
Standard thicknesses and mixes
Internal walls are typically plastered 12 mm thick; external walls, which need to shed water and resist weathering, go to 15 mm; rough surfaces, uneven masonry or ceilings sometimes need 20 mm or a two-coat application. A 1:6 cement:sand mix (1 part cement to 6 parts sand) is standard for internal plastering; external work often steps up to a richer 1:4 or 1:5 mix for extra durability.
How this is calculated
Wet volume is simply area × thickness — for a 100 sq m wall at 12 mm, that's 100 × 0.012 = 1.2 cubic metres of wet plaster. Multiply by the standard 1.33 dry-volume factor to get the dry cement + sand you need to buy (plaster shrinks as it's mixed and troweled on, same principle as concrete's 1.54 factor, just a smaller correction since plaster is a thinner, less aggregate-heavy mix).
That dry volume is split into cement and sand by the mix ratio: cement's share is 1 ÷ (1 + sand parts) of the dry volume — for 1:6, that's 1/7. Cement volume converts to bags the same way as the concrete calculator (× 1440 kg/m³, ÷ 50). An optional +20% allowance is available on top for uneven or heavily keyed surfaces that soak up extra material.
Worked example: 100 square metres
For 100 m² of internal wall at 12 mm thickness, 1:6 mix, no extra wastage allowance:
Wet volume = 100 × 0.012 = 1.2 m³ Dry volume = 1.2 × 1.33 = 1.596 m³ Cement volume = 1.596 ÷ 7 = 0.228 m³ → 0.228 × 1440 ÷ 50 = 6.6 bags Sand = (1.596 − 0.228) × 35.3147 = 48 cft
Internal vs external plastering
Internal plastering focuses on a smooth, paint-ready finish and can use a leaner 1:6 mix at 12 mm. External plastering has to survive sun, rain and temperature swings — it's usually thicker (15 mm), richer (1:4 or 1:5), and often finished with a weatherproof texture or a waterproofing admixture. Never use the same batch specification for both without checking; under-specifying external plaster is one of the most common causes of early wall dampness and cracking.
Frequently asked questions
How many cement bags for plastering 100 sqm?
About 6.6 bags of cement and 48 cft of sand for 100 square metres at 12 mm thickness in a 1:6 mix — see the worked example above.
How much cement and sand is needed for plastering 1000 sq ft?
1,000 sq ft is about 92.9 m². At 12 mm thickness in a 1:6 mix, that works out to roughly 6.1 cement bags and 45 cft of sand — slightly less than the 100 m² example since 1,000 sq ft is a touch smaller than 100 m².
What thickness should internal plastering be?
12 mm is standard for internal walls. External walls are usually done at 15 mm, and rough or uneven surfaces sometimes need 20 mm.
What is the standard plastering mix ratio?
1:6 (cement:sand) for internal plastering; 1:4 or 1:5 for external plastering, where extra cement improves weather resistance.
Why does the dry volume use 1.33 and not 1.54 like concrete?
Both correct for the same effect — dry materials taking up more space than compacted wet material — but plaster is a thinner cement-sand mortar without coarse aggregate, so it needs a smaller correction factor than full concrete.
Building on your own land?
Building vs. buying — the real comparison
This calculator is for people building on land they already own. If you're still deciding between building yourself and buying a finished flat, this comparison covers the real costs and timelines of both.