Paint Quantity from Coverage Rate
Also known as how much paint · paint needed · gallons of paint
Worked example: 90 m2, two coats, 36 m2 per pail → 5 pails — press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Try different units for next level excitement!
Paint Quantity from Coverage Rate explained
Coverage, not volume, is what the label tells you and what you should calculate with. A US gallon of wall paint traditionally covers about 400 ft², a 3.78 L can about 37 m², so the sum is area times coats divided by coverage. Two coats is the realistic default for anything but a repaint in the same colour, and going from a dark colour to a light one can mean three.
Treat the label figure as optimistic. It assumes a smooth, sealed, previously painted surface. Bare drywall drinks the first coat, textured or stucco walls can cut coverage by a third, and rough masonry by half. Spraying wastes more than rolling, especially outdoors. If in doubt, work out the area first and then buy to the next whole container, because a second trip for a half litre of a tinted colour risks a batch that does not quite match.
Measuring the area is where the real errors hide. Take wall length times ceiling height for each wall, and subtract only the doors and large windows. Trying to deduct every small opening is false economy, and the leftover is what you keep for touch-ups.
Paint Quantity from Coverage Rate formula
- = Containers needed
- = Surface area (m²)
- = Number of coats
- = Coverage per container (m²)
Missing one of these? Work it out first, then come back
- Containers needed — Sheets or Tiles Needed (with Waste Allowance), Stair Riser Count from Total Rise
- Surface area — Roof Area from Footprint and Pitch, Cone Total Surface Area
- Number of coats — Stair Riser Count from Total Rise, Stair Total Run from Risers and Tread Depth
- Coverage per container — Roof Area from Footprint and Pitch, Sheets or Tiles Needed (with Waste Allowance)