Painting Calculator (Primer + Paint Coverage)
Estimate primer and paint litres, plus total cost in NPR/INR/PKR, from wall area, number of coats, coverage rate, and unit price.
Wall area and coats
Coverage and pricing
How this works
Primer and paint litres are independent quantities, each driven by their own coat count and coverage rate. Cost is the sum of the two product lines:
primerL = wallArea × primerCoats / coveragePrimer
paintL = wallArea × paintCoats / coveragePaint
primerCost = primerL × pricePerL_primer
paintCost = paintL × pricePerL_paint
totalCost = primerCost + paintCostCoverage rates are manufacturer-published values for a single coat on a smooth surface — rough or porous walls drink more, so derate by 10–15 percent for unprimed plaster or block walls.
Worked example
100 m² wall, 1 primer coat at 8 m²/L, 2 paint coats at 10 m²/L, primer at NPR 250/L, paint at NPR 450/L:
- Primer =
100 × 1 / 8 = 12.5 L - Paint =
100 × 2 / 10 = 20 L - Primer cost ≈ NPR 3,125
- Paint cost ≈ NPR 9,000
- Total ≈ NPR 12,125
Sources
- Manufacturer-published coverage rates (Asian Paints, Berger, Nerolac data sheets); IS 5410 (cement primer specification)
FAQ
What coverage rates should I enter?
Manufacturer data sheets quote 8–10 m²/L for cement primer on smooth plaster and 9–12 m²/L for water-based emulsion paint per coat. Solvent-based enamels are richer and cover only 12–14 m²/L per coat. The defaults (8 for primer, 10 for paint) cover most interior emulsion jobs. Derate by 10–15 percent on rough or porous walls because they absorb more material.
How many coats should I plan for?
One primer coat is the standard for plastered or putty-finished walls — primer's job is to seal porosity and give the topcoat something to grip. Two paint coats are the residential default; the first coat builds the colour and the second levels the sheen. For dark-on-light colour changes or rough textures plan three paint coats; for ceilings of bathrooms and kitchens consider an extra primer coat for moisture sealing.
Does the calculator account for openings and exclusions?
Not automatically — enter the net wall area you actually need to paint. Subtract the area of doors, windows, and any other unpainted surface from the gross wall area before entering it. A common shortcut for residential rooms is to multiply room floor area by 3.5–4.0 to estimate net wall and ceiling paintable area; for a precise figure, measure each wall and subtract openings.
Why is total cost split into primer and paint?
Primer and paint have very different per-litre prices and coverage rates, so showing them separately makes the cost driver obvious. If the primer cost surprises you, check the coverage rate — a thin or watery primer covers only 5–6 m²/L and inflates the litres needed quickly. The total cost is just the arithmetic sum of the two lines so you can audit each independently.
Does changing the currency convert NPR to INR or PKR?
No. The currency selector is a labelling change only. The numeric figures stay exactly the same — only the currency code in front of them changes. Enter prices in your chosen currency directly. The calculator does not perform any foreign-exchange conversion or apply local taxes.
What about texture, sheen, or specialty finishes?
Texture finishes (sand textures, putty effects), metallic and pearl paints, and waterproof exterior coatings all have lower coverage rates — typically 5–8 m²/L per coat — and higher per-litre prices. Enter the manufacturer's coverage and the actual price you've quoted. The arithmetic is the same; the calculator does not assume any specific product or finish.