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Plaster Calculator

Cement and sand for wall plaster — by thickness and mix, with the working shown.

Construction● Free Formula shown Rates dated
Quick Answer

Plastering 100 sq ft at 12 mm in a 1:6 mix needs about 0.63 bags of cement and 4.9 cft of sand — so 1,000 sq ft takes roughly 6.3 bags and 49 cft, wastage included. External faces at 15–20 mm in a richer 1:4 or 1:5 mix need about 1.5–2.3× as much cement over the same area. Enter your wall below for exact quantities, the full working and a dated cost.

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The Formula

Plaster materials = net area × thickness × 1.33 (dry factor), split in the cement : sand ratio, + published wastage

Wet mortar is denser than the loose ingredients that go into it, because the cement paste and water fill the air voids between sand grains and damp sand shrinks as it is mixed. You therefore buy about a third more dry material than the finished plaster volume — that is the 1.33 factor. Cement volume converts to bags at 0.0347 m³ (1.226 cft) per 50 kg bag.

Assumptions & Wastage

  • Wet plaster volume = net wall area × thickness. Standard thicknesses: 6 mm for RCC ceilings and soffits, 12 mm for internal walls, 15 mm for external single-coat, 20 mm for rough external or two-coat work
  • Dry volume = wet volume × 1.33, covering the voids in loose sand and the bulking of damp sand — the same factor this site uses for brick mortar, so the two calculators agree
  • Published references use 1.27 to 1.35 for this factor, and some treat it as already including wastage. This calculator uses 1.33 and then adds the material wastage below separately, which makes it slightly conservative — it will not under-order
  • Mix ratios follow Indian site practice: 1:6 for internal walls, 1:5 or 1:4 for external faces, 1:3 for repairs and waterproof pointing
  • One cement bag = 50 kg ≈ 0.0347 m³ at 1,440 kg/m³ bulk density
  • Costed at the PPC rate — PPC is the cement normally used for plaster and masonry; OPC of the same brand runs ₹30–40/bag higher
  • Cement is sold in whole bags, so the cost line rounds the bag requirement up. The bag figure itself is shown unrounded so you can total several walls before buying
  • Wastage is added on the computed base quantities using the published allowances below — nothing is pre-included, so do not add wastage again
  • Openings you enter are deducted in full. Measurement practice makes no deduction for very small openings and only a part deduction for larger ones, because reveals and jambs still get plastered — so on a wall with many small windows, deduct conservatively or not at all
MaterialWastage allowance
cement3%
sand10%

Worked Examples

10 × 10 ft internal wall, both faces, 12 mm, 1:6

  1. Net area: 10 × 10 ft − 0 sq ft openings = 100 sq ft per face × 2 faces = 200 sq ft
  2. Wet mortar: 200 sq ft × 12 mm = 7.87 cft = 0.223 m³
  3. Dry volume: 0.223 × 1.33 = 0.297 m³ (the extra third covers voids and sand bulking)
  4. Cement: 0.297 ÷ 7 = 0.0424 m³ ÷ 0.0347 m³/bag = 1.22 bags; +3% wastage = 1.3 bags
  5. Sand: 0.297 × 6/7 = 8.98 cft; +10% wastage = 9.9 cft
  6. Material cost: ₹1,152 to ₹1,886 (as of Jul 2026), costing 2 whole cement bags

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30 × 10 ft external wall, one face, 20 mm, 1:4

  1. Net area: 30 × 10 ft − 0 sq ft openings = 300 sq ft per face × 1 face = 300 sq ft
  2. Wet mortar: 300 sq ft × 20 mm = 19.69 cft = 0.557 m³
  3. Dry volume: 0.557 × 1.33 = 0.741 m³
  4. Cement: 0.741 ÷ 5 = 0.1483 m³ ÷ 0.0347 m³/bag = 4.27 bags; +3% wastage = 4.4 bags
  5. Sand: 0.741 × 4/5 = 20.94 cft; +10% wastage = 23 cft
  6. Material cost: ₹2,782 to ₹4,534 (as of Jul 2026), costing 5 whole cement bags

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Rates & Model Data Used

Every number below is a range with a date — material prices in India move quickly, so always check the "as of" month before relying on a figure.

ItemRate / valueAs ofNote
Cement (PPC)₹280–400 / bag (50 kg)Jul 2026Re-baselined 2026-07-24 from ₹330–400. The discount over ordinary Portland is roughly double what this entry used to publish: PPC runs ₹30–40/bag below the SAME brand's OPC, not ₹10–30. Eight same-brand pairs in Bangalore average −₹33.75 (median −₹35) and seven in Hyderabad average −₹35.00 (median −₹30); both hold up after dropping the one wild pair and any duplicated line, and CPWD's Clause 10CA Dec 2025 base prices give −₹33.90/bag ex-GST (−₹40 grossed at 18%) as corroboration. Note the wide top: premium blended products such as ACC Suraksha Power and UltraTech Weather Plus sell at ₹375–400 and are priced as premium goods, not as the cheap alternative to their own maker's OPC — so the ₹30–40 saving is a same-brand, same-shop comparison, and the band ceiling sitting only ₹15 below OPC's is not a contradiction of it. The ₹280 floor is a value-brand observation, not an ordinary counter price: stripped of GST it sits about 6% above CPWD's 2023 bulk ex-carriage Delhi base once the measured PPC differential is applied, which leaves almost nothing for freight and margin and is only possible near a plant. Preferred for masonry and plaster, and code-legal for RCC — IS 456:2000 cl. 5.1 lists PPC among the cements permitted for plain and reinforced concrete — but cl. 13.5.1 asks for at least 10 days of wet curing where blended cements are used, against 7 for ordinary Portland. Same inferred GST-inclusive basis, same 28% → 18% history and the same geographic thinness as the OPC entry; medium for those reasons.
River sand₹60–110 / cftJul 2026Re-anchored 2026-07-25: the three content farms (HouseYog, Civiconcepts, Varna Homes) that used to back this band are struck; it now rests on two government schedules read firsthand — but be clear about what they anchor. CPWD DAR 2023 applies coarse sand (zone III, natural) at ₹1,450/cum throughout its own concrete and mortar rate analyses = ₹41/cft ex-GST, ₹43/cft incl. 5% GST (a stray basic-rate index line at ₹285/cum is an anomalous layout artifact, not the applied rate; the '₹1,450 = spirit/air-compressor' reading is a coincidental-value misread — the operative applied rate is ₹1,450). Maharashtra PWD SSR 2022-23 (p.541) gives natural/VSI/artificial sand ₹1,670/cum = ₹47/cft, crushed ₹1,200/cum = ₹34/cft, screened natural (plaster) ₹1,781/cum. So the government evidence pins an EX-GST, EX-CARRIAGE, AT-SOURCE rate of ~₹41–47/cft (~₹43–50 incl. GST at yard) — and that is ALL it pins. The ₹60 floor is that yard rate plus a minimum ~₹15/cft lead (matching delivered Delhi ≈ ₹50–65); it is lowered from ₹70, which came only from the now-struck per-tonne blog quotes. The ₹110 ceiling is deliberately NOT re-sourced — no primary or retail anchor exists above ₹70 now — and the whole upper half is extrapolation (source rate + heavy lead + retail margin + documented 30–50% mining-ban and monsoon spikes). That is exactly why this is medium, not high, and why the carriage bridge from source to delivered is a fitted, unverified step, disclosed as such. Do not cite the schedules as proof of the delivered band; they anchor only the floor. South metros (Bangalore/Chennai/Hyderabad) sit at the ceiling and above, North plains and near-river Maharashtra at or below the floor; transport adds ₹15–40/cft. Unit exactness is the classic sand failure: confirm cft vs brass (1 brass = 100 cft = 2.83 cum) vs tonne vs truckload and whether transport is in the quote; 1 cum = 35.3147 cft. Density (resolved, unchanged): 22–24 cft/t (1,470–1,600 kg/m³) from IS 2386 Pt III, classical tables and trade 1 brass ≈ 4.5 t — do NOT cite IS 383 for density, it grades aggregate, it does not weigh it. GST 5% (natural sand HSN 2505), asserted from the standing schedule and NOT re-verified against a CBIC notification this pass — flagged. State sand portals (Telangana TGMDC, AP) are JS booking apps that expose no static notified rate.
M-sand (manufactured)₹45–75 / cftJul 2026Re-anchored 2026-07-25; content farms (HouseYog, Civiconcepts, Varna Homes) struck. ₹45–75/cft delivered retail incl. 5% GST, the South- and West-India default. Government anchor — Maharashtra PWD SSR 2022-23 (ex-GST, ex-carriage): crushed sand ₹1,200/cum (₹34/cft) and VSI/artificial ₹1,670/cum (₹47/cft) against natural screened ₹1,781/cum; +5% GST and ₹15–40/cft carriage bridge these to the delivered band, and the SSR's own contractor crushed-sand work-item (incl. labour, ≤5 mm) at ₹1,859/cum = ₹53/cft corroborates the upper zone. Cheaper than river sand: standard crushed M-sand runs ~28–33% below natural sand in the SSR itself, and the gap widens in the South where river sand carries mining-ban scarcity premiums — but note VSI premium-grade M-sand is priced level with natural sand, so the saving is a standard-grade, same-market comparison, not universal. Delhi CPWD DAR 2023 carries no quarry-M-sand line, only recycled-RCA manufactured sand at ₹1,400/cum, which confirms M-sand as a South/West material. Consistent gradation, no monsoon or mining-ban seasonality. Same honest limit as the river entry: the government schedules anchor only the ex-GST at-yard floor (~₹36 crushed); the ₹75 ceiling and the delivered span above the floor rest on a modelled carriage bridge, not observed Southern retail — hence medium, and the anchor is Western/Delhi and 2022-23 vintage. GST 5% (HSN 2517), asserted from the standing schedule, not re-verified against CBIC this pass.

How to Use This Calculator

  1. Measure the wall. Length and height in feet, and the total area of doors and windows. Run the calculator once per wall and add the bag figures — they are shown to one decimal so they total correctly.
  2. Choose faces and thickness. Internal partitions get plastered both sides; an external wall face counts once. Use 12 mm internally, 15–20 mm externally, 6 mm on RCC ceilings.
  3. Pick the mix. 1:6 for internal walls, 1:4 or 1:5 for external and damp-exposed faces, 1:3 for repairs and waterproof pointing.
  4. Check the working. Every step is shown under the result, and the rates used are dated in the table below. Verify the numbers against your contractor's estimate before ordering.

Frequently Asked Questions

How much cement and sand is needed for 100 sq ft of plastering?
For 12 mm plaster in a 1:6 mix, about 0.63 bags of cement (roughly 31 kg) and 4.9 cft of sand, with this calculator's 3% cement and 10% sand wastage already added. At 15 mm in 1:5 the same 100 sq ft needs about 0.92 bags and 6.0 cft; at 20 mm in 1:4 it rises to about 1.47 bags and 7.7 cft.
What is the 1.33 dry volume factor in plastering?
Loose sand contains air voids and bulks further when damp. Mixing fills those voids with cement paste and water, so producing 1 m³ of finished wet plaster consumes about 1.33 m³ of loose dry ingredients. Published Indian references use 1.27 to 1.35; this calculator uses 1.33 and shows it in the working, and it adds material wastage on top rather than assuming the factor already covers it.
Which plaster thickness and mix should I use where?
Internal walls take 12 mm in a 1:6 mix. External walls take 15 mm single-coat or 20 mm where the brickwork is rough or two coats are specified, in a richer 1:4 to 1:5 mix so the face resists rain. RCC ceilings and soffits need only 6 mm because the concrete surface is already smooth. Repairs, pointing and waterproof patches use 1:3.
How much plaster does a 1,000 sq ft house need?
Plaster area typically works out to 3–4 times the built-up area once you count both faces of every internal wall, the external faces and the ceilings. For a 1,000 sq ft floor that is roughly 3,000–4,000 sq ft of plaster — about 19–25 bags of cement and 150–200 cft of sand at 12 mm in 1:6, and more where the external faces are 20 mm in a richer mix. Measure wall by wall for anything you are ordering against.
Can I use M-sand for plastering?
Yes, but only plastering-grade M-sand — sold as P-sand — not the coarser concrete-grade M-sand. Ordinary M-sand gives a harsh mix that is hard to finish and more prone to surface cracking. P-sand is typically 15–30% cheaper than river sand (₹45–75/cft against ₹60–110/cft as of Jul 2026) and avoids the monsoon supply bans river sand is subject to.
How much water does plaster need?
This calculator does not output mixing water, because plaster consistency is judged on site and depends on how damp the sand already is — masons use roughly 20–30 litres per bag of cement. The number that actually decides whether plaster cracks is curing water: keep the finished surface damp for at least 7 days. Plaster that is allowed to dry out in the first week will craze regardless of how correct the mix was.
Why is my mason's estimate higher than this?
Three common reasons. Uneven brickwork forces an average thickness well above the nominal 12 mm, and thickness drives quantity linearly. Rebound and droppings on a rough or overhead surface waste more than the 10% sand allowance assumes. And a quoted rate usually bundles labour, scaffolding and curing, which this calculator excludes — it estimates material only.
Does this include labour, scaffolding or chicken mesh?
No. This is the cement and sand for the plaster itself. Labour is normally quoted per sq ft and varies widely by city; scaffolding, chicken mesh at junctions between brick and RCC, waterproofing admixtures and any putty or primer that follows are all separate line items in a real estimate.

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Sources & Limitations

What this calculator does not model

  • Estimates material only — labour, scaffolding, curing, chicken mesh, waterproofing admixtures, putty and primer are all excluded
  • One rectangular wall per run; total several runs for a room or a floor
  • Assumes the nominal thickness is achieved. Out-of-plumb or uneven brickwork can push the real average thickness well past it, and the quantity rises in direct proportion
  • Does not model two-coat work as separate base and finish mixes — enter the total thickness and the governing mix
  • Gypsum and ready-mix plasters are not covered; this is cement-sand plaster only
  • Delivered material prices vary by state and season; the cost band uses the dated national ranges below