Paint Coverage Calculator
Enter the room length, width and height, subtract doors and windows, set the paint coverage rate and number of coats, and get the litres needed — rounded up to common retail can sizes (1 L / 5 L) so you can buy without coming up short. Defaults match a typical Hong Kong bedroom: 4 × 5 × 2.7 m, two coats of emulsion at 11 m²/L.
Please enter a valid number
Litres to buy
8.0 L
Exact requirement
7.93 L
Total area ÷ coverage; before rounding up.
Paintable surface
43.6 m²
Rounded up to the nearest 0.5 L for a buffer. Actual usage depends on substrate porosity, base colour and application technique.
Formula
Paint = ((2 × (L + W) × H + ceiling) − openings) × coats ÷ coverage_per_litre
- · Wall area = 2 × (length + width) × height; ticking "include ceiling" adds length × width.
- · Paint per coat = wall area ÷ coverage; total = per coat × number of coats.
- · Interior emulsion typically covers 10–13 m²/L per coat (Dulux & Nippon Paint Hong Kong datasheets). Undercoat ≈ 14 m²/L; gloss / top coat ≈ 16 m²/L.
- · Two coats is the industry minimum: pale fresh walls may finish in two; strong colour changes or stains often need three.
- · Litres-to-buy is rounded up to the nearest 0.5 L to leave a small buffer. Actual usage depends on substrate porosity, base colour and roller technique.
- · Sources: Dulux Trade datasheets, Nippon Paint Vinilex specs, Crown Paints application guide.
Frequently asked
Will one 5-litre tin be enough for my room?
A 5 L tin of emulsion (11 m²/L, two coats) covers about 22–23 m² of wall. A typical small HK bedroom of 3 × 3.5 × 2.7 m has ≈ 35 m² of wall, so two coats need ≈ 6.4 L — one 5 L tin alone is usually short. Enter your dimensions and the tool will tell you exactly how much to buy.
Why don’t you subtract the skirting board or cornice?
Skirting boards (4–10 cm tall) and cornices are normally finished in gloss or trim paint, not the wall emulsion. If you’re only painting the walls, you can leave them in — they’re usually masked off rather than counted. If you do want to deduct them, add their area to the "doors & windows" field.
How many extra coats do I need to go from a dark colour to a lighter one?
Covering a dark colour (deep blue, red, wine) with a lighter one usually means one or two coats of white undercoat plus two top coats — 3 to 4 coats total. Set "coats" to 3 or 4 and the calculator will scale the litres accordingly.
Where do I find the coverage rate (m²/L) for my paint?
Every paint tin and manufacturer technical data sheet (TDS) lists a "spreading rate" in m²/L or m²/kg. Dulux Diamond interior emulsion and Nippon Vinilex both spec 10–13 m²/L per coat. If you can’t find one, pick the "interior emulsion" preset (11 m²/L) for a safe default.
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