How to Calculate Paint Quantity
Calculating paint quantity before buying prevents waste and avoids running short mid-project. The formula is: paintable area (㎡) ÷ coverage rate (㎡/L) × number of coats + 10% waste = liters needed. Wall area equals room perimeter × ceiling height, minus door and window areas.
Door area is deducted at approximately 2×2m = 4 ㎡ each, and each window at approximately 1.2×1.2m = 1.44 ㎡. A 10% buffer is included automatically for touch-ups and uneven application.
Paint Type Selection Guide
- Interior latex: Low odor, fast drying. Ideal for bedrooms and living rooms.
- Exterior: UV and moisture resistant. For outdoor walls only.
- Oil-based: High durability, glossy finish. Good for bathrooms and kitchens.
- Ceiling paint: Anti-drip formula. White-only in most products.
Frequently Asked Questions
New drywall or highly porous surfaces require a primer coat. Budget for the same square footage as your paint. Primer improves adhesion and can reduce the number of finish coats needed.
Properly sealed latex paint lasts 2–5 years in storage. Keep lids tight, store upright in a cool, dry place away from freezing temperatures.