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Calculate paint quantities needed for walls and surfaces. Supports primer, interior, exterior, and enamel paints with multiple coats. Free construction calculator.
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Calculate the exact number of litres of paint for any room, exterior, or surface — accounting for coats, coverage rate, and wastage.
Paint coverage is calculated from the spread rate (theoretical coverage per litre) reduced by a wastage factor for surface porosity, roller splatter, brush waste, and uneven application. Practical coverage is typically 80–90% of the theoretical rate stated on the tin.
The total area to paint is wall area + ceiling area − window and door openings. Apply this for each coat required. New plaster needs a mist coat (50:50 diluted emulsion) before the full-strength coats — this coat seals the porous surface and prevents topcoat failure.
Multiply litres by number of coats to get total litres. Then divide by the tin size (typically 2.5 L, 5 L, or 10 L) to get the number of tins to buy. Always round up to the next full tin — opening a partial tin to finish is far cheaper than running out mid-coat.
A = 2×(L+W)×H + (L×W) − OpeningsAll walls + ceiling. Subtract each door (≈1.8×2.0 m = 3.6 m²) and window (≈0.9×1.0 m = 0.9 m²) from total area.
L_coat = A ÷ (Spread Rate × Efficiency)Efficiency = 0.80–0.90 for brush/roller. Use 0.80 for rough/porous surfaces; 0.90 for smooth plaster. Manufacturer spread rate already at 100% efficiency.
L_total = L_coat × Number of CoatsNew plaster: mist coat (diluted, ÷1.5 coverage) + 2 full coats. Repaint: 1–2 coats. Dark to light colour change: 2–3 coats. Always add 10% contingency.
Tins = Ceil(L_total ÷ Tin Size)Common sizes: 1 L, 2.5 L, 5 L, 10 L. Buy the largest size that covers your area to minimise cost per litre. Large pails (15–20 L) available trade for big projects.
| Type | Spread Rate | Drying Time | Application | Coats Needed |
|---|---|---|---|---|
| Matt emulsion | 10–12 m²/L | 1–2 hrs recoat | Interior walls & ceilings | 2–3 |
| Silk / satin | 11–13 m²/L | 2–4 hrs recoat | Kitchens, bathrooms (wipeable) | 2 |
| Eggshell | 12–14 m²/L | 4–6 hrs recoat | Woodwork, architraves, doors | 2 |
| Gloss (oil) | 12–14 m²/L | 16–24 hrs recoat | Exterior woodwork, metalwork | 2–3 |
| Masonry paint | 5–8 m²/L | 4–6 hrs recoat | Exterior brick, render, concrete | 2 |
| Primer / undercoat | 8–10 m²/L | 2–4 hrs recoat | New surfaces, colour change | 1 |
Cave paintings at Lascaux and Chauvet used ochre, charcoal, and animal fat as paint — the world's first known use of pigment as a coating. These natural pigments have lasted over 40,000 years, proving their durability.
Egyptians used lime-based whitewash and coloured mineral pigments for interior wall decoration. Lapis lazuli (blue), malachite (green), and cinnabar (red) were ground into powder and mixed with egg or gum arabic as binder.
Lead white (basic lead carbonate) dominated house paint in Europe and America. Applied in linseed oil, it provided excellent coverage and durability but was extremely toxic. Lead paint was later banned for residential use in the 1970s (USA) and 1980s (UK).
Sherwin-Williams co-founded (1866) and Pratt & Lambert (1849) produced the first commercially prepared ready-to-use oil paints in tin cans, replacing the practice of mixing paint on-site from raw pigment and oil.
Synthetic latex (water-based emulsion) paints introduced, offering fast drying, low odour, and easy clean-up with water. By 1960 latex overtook oil-based paints in the residential market.
Low-VOC and zero-VOC paints became mainstream, driven by indoor air quality regulations. Nano-technology paints (self-cleaning, anti-bacterial, thermal-reflective) now available for specialist applications.
Indian Standard for dry distemper including composition, consistency, spreading capacity, and lightfastness requirements for interior wall decoration.
Read source →British Standard specifying performance requirements for weatherproof exterior masonry coatings including water vapour permeability, water absorption, and adhesion.
Read source →Standard practice for determining volatile organic compound content of paints and coatings, supporting compliance with environmental air quality regulations.
Read source →One coat of paint is enough if it's a quality brand
Even premium paints require 2 coats for uniform colour and opacity, especially on new surfaces, light over dark, or porous substrates. One coat leaves thin spots over surface texture and colour variation at joins.
You can use the same paint for walls and trim
Wall paints (matt/silk emulsion) lack the hardness to resist scuffs on trim/woodwork. Trim requires eggshell or gloss finish with higher resin content for durability. Using wall paint on skirting boards will show marks within weeks.
More expensive paint always covers better
Coverage (m²/L) is primarily a function of pigment load and titanium dioxide content, not price. Some own-brand paints have excellent opacity. Check the theoretical coverage on the tin — ≥11 m²/L is the key metric, not marketing claims.
Adding water to paint improves coverage
Thinning with more than 10% water reduces pigment concentration, lowering opacity and coverage. A mist coat (10% dilution) is used on new plaster only as a sealer, not as a painted finish. Always follow manufacturer thinning guidance.
Accurate paint estimation saves money and reduces waste on every decorating project.