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Putty Quantity Calculator

Area × coats × consumption to bags.

Quick answer

With the default inputs: Area 200 m² · Coats 2 coats · Putty type Water resistant etc.Total putty 540 kg

Edit the inputs below to recalculate.
Length LWidth W
Area × coats × unit rate; internal and external corners are extra.

Inputs

m²
coats

Result

Total putty
540kg
Consumption per coat1.35kg/m²
Coats2coats
Total per m²2.70kg/m²
Bags (whole)27bags
Purchased weight540kg

Consumption figures are empirical: water-resistant putty about 1.2-1.5 kg/m² per coat, standard 0.8-1.0, gypsum levelling 1.8-2.5. Losses come from substrate absorption (fresh plaster drinks a lot) and levelling thickness on uneven walls. Wet areas such as kitchens, bathrooms and basements must use water-resistant (type N) putty; standard putty powders and falls off in damp - the usual cause of peeling walls a year after decoration.

Formula

Per coat = base consumption × substrate factor
Total = per coat × coats × area
Bags = ceil(total ÷ bag size)
200 m² of cement plaster with two coats of water-resistant putty: 1.35 kg/m² per coat, 2.70 per m², 540 kg total, 27 bags of 20 kg. On a rough wall (1.3 factor) it becomes 702 kg and 36 bags.

How to work it out

  1. Establish the skimming area: walls (perimeter × clear height − openings) plus ceilings; balconies and corridors separately.
  2. Set the unit rate by substrate: bare concrete 1.8-2.2 kg/m² per coat, cement render 1.2-1.6, plasterboard or gypsum 0.8-1.2.
  3. Multiply by the number of coats. Two coats plus sanding is standard; three where flatness is poor or wallpaper follows.
  4. Divide by the bag weight and round up, keeping 5% for corners and making good around sockets.
  5. Buy water-resistant and standard putty separately: type N for bathrooms, kitchens and basements, type Y elsewhere.

Where it goes wrong

Material and cost

Standard putty 25-45 CNY per 20 kg bag, water resistant 40-70. Labour with sanding 8-15 CNY/m²; full preparation including stripping and primer 20-35 CNY/m².

On site

Basis

FAQ

Why is water-resistant putty both dearer and heavier to use?
It contains more redispersible polymer and water repellent, is denser and covers better, so more material goes on per square metre. It also resists damp, does not powder or shell off - essential in humid regions and around kitchens and bathrooms. The saving on material is nothing against one redo.
How many coats, and can one thick coat do?
Two: the first levels, the second tightens. A single thick coat dries unevenly - skin first, core later - and cracks while it shrinks, and sands through easily. Codes limit each coat to about 1 mm of water-resistant putty and total thickness to 2-3 mm; beyond 5 mm it may detach, so level with gypsum plaster or mortar first.
Putty versus gypsum levelling?
Gypsum levelling plaster handles large thicknesses - 5-20 mm in one go - with high strength and fast drying, but poor water resistance, so dry interiors only. Putty is a 2-3 mm finish coat. The order is substrate preparation, gypsum levelling, putty, primer, topcoat. Using putty to fill a 10 mm hollow will always crack.

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Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Putty Quantity Calculator. 2026-10-25. https://jianzhujisuan.com/en/putty-quantity

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.