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About this tool
Estimate litres of exterior emulsion from wall area, coats and surface porosity, with pack sizes and material cost.
The Exterior Wall Paint Quantity Calculator converts wall dimensions into litres of exterior emulsion using the standard trade relation litres = paintable area x coats / spreading rate. It starts from the 100-140 sq ft per litre per coat that Indian exterior emulsion data sheets quote for smooth plaster, then scales that rate down for porous, sand-faced, textured or bare masonry surfaces. Homeowners get a shopping list of tin sizes and a material cost; contractors get a defensible number to quote against.
Open Exterior Wall Paint Quantity Calculator on AltFTool — it loads instantly in your browser.
Choose Perimeter x height or I know the area, then fill Total wall length / perimeter (ft) and Wall height (ft) — or Gross wall area (sq ft) — plus Windows, doors and grilles to deduct (sq ft).
Set Number of finish coats (2 by default, up to 6), pick the Surface condition option that matches the wall — Repaint over sound old paint, Smooth cement plaster (primed), Bare / new cement plaster, Sand-faced or rough plaster, Textured / exterior texture finish or Exposed brick or block work — and adjust Wastage allowance (%) and Emulsion price (INR per litre).
Paint required shows the litres over rows for Paintable area, Effective coverage in sq ft / L / coat, Tins to buy, Left over after the job, Material cost and Cost per sq ft of wall, plus a Two ways to buy it table comparing Least paint bought with Fewest tins to carry in 20, 10, 4 and 1 L packs. Copy result copies the estimate.
Applies a factor for texture and porosity instead of using one flat spreading rate.
Turns the litre figure into the exact 20 L, 10 L, 4 L and 1 L packs to buy.
Windows, doors and grilles come off the gross area before any paint is costed.
Around 100-140 sq ft per litre per coat on smooth, primed cement plaster, which is the band printed on most Indian exterior emulsion data sheets. On rough sand-faced plaster expect roughly 70-90 sq ft, and on textured finishes it can drop below 70 sq ft per litre per coat.
Two finish coats over a primed surface is the standard specification for exterior emulsion, and it is what most manufacturer warranties assume. A third coat is worth it only for a strong colour change, a deep shade going over white, or a chalky old surface.
Yes, deduct any opening you are not painting. Rule of thumb sizes are about 21 sq ft for a standard 3 ft x 7 ft door and about 15 sq ft for a 4 ft x 4 ft window, but measuring the actual openings gives a far better estimate on a facade with a lot of glazing.
On bare or newly plastered exterior walls, yes - an exterior primer seals the surface so the emulsion is not absorbed unevenly, and it is what makes the quoted spreading rate achievable. A sound, previously painted wall that is clean and not chalking can usually be recoated without a full primer coat.
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