Buy too little paint and you need a second can mid-job. Buy too much and you store it for a decade. Here's the math.
Most people learn the formula once in school and never touch it again — until life forces them to. Buy too little paint and you need a second can mid-job. Buy too much and you store it for a decade. Here's the math.
Wall area = perimeter × height − doors/windows. Divide by paint coverage per litre.
Most emulsions cover 12–14 m²/L for one coat. Two coats are standard for colour changes.
Always add 10% for touch-ups and cut-ins. Better than a midnight hardware-store run.
How much for a 3×4 m room? Walls ~50 m² + ceiling 12 m² = ~62 m². Two coats ≈ 10 L.
Is primer always needed? Yes for new drywall, big colour changes, or stained walls. Coloured primer reduces topcoats.
Bookmark the calculator linked above — you will need it more often than you think.