Paint Calculator
Enter your room size to estimate how much wall paint to buy.
How it's calculated
- Walls: 2 × (length + width) × height for a whole room, the sum of width × height for separate walls, or the area you enter.
- Subtract doors and windows: 1.9 m² (21 ft²) per standard door and 1.5 m² (15 ft²) per standard window, or the width × height of each custom opening.
- The ceiling (length × width) is added to the wall paint if it's the same color, or calculated separately with its own coats and coverage.
- Paint = area × coats ÷ coverage. Most wall paints cover about 10 m²/L (350 ft²/gal) per coat. Check the label on your can.
- Several rooms: each room uses its own coats, coverage and ceiling color, is rounded up on its own, and then the amounts are added.
- Cans: the set with the lowest typical price that holds at least that much paint. Bigger cans cost less per liter, so a little paint may be left over.
The result is rounded up. Textured or porous walls and dark-to-light color changes may need more paint.
Frequently asked questions
How much paint do I need for a room?
For a 4 × 3 m room with 2.5 m walls, one door and one window, two coats need about 6.4 L of wall paint. A 12 × 10 ft room with 8 ft walls needs about 1.9 gal. Enter your own sizes in the calculator above for an exact amount.
How many coats of paint should I use?
Two coats for most walls: the first evens out the surface, the second gives the final color. One coat can be enough to refresh the same color with a good paint. New plaster or drywall and big color changes usually need a primer first.
How much does a gallon or liter of paint cover?
Most interior wall paints cover about 10 m²/L (350 ft²/gal) per coat. Textured or porous surfaces take more, so check the coverage on the can and enter it in the calculator.
Should I subtract doors and windows?
Yes, for an accurate amount. The calculator subtracts 1.9 m² (21 ft²) per standard door and 1.5 m² (15 ft²) per standard window, or the exact size of each custom opening. In a room with few openings, skipping this leaves you a small reserve.
How much paint do I need for the ceiling?
The ceiling area is its length × width. Ceilings are often painted with a separate flat white paint: turn on the ceiling, choose “Different color” and set its own coats and coverage. If it's the same paint, the calculator adds the ceiling to the wall paint.
Should I buy extra paint?
The result is already rounded up, and the suggested cans usually leave a little over. Keep the leftover for touch-ups, and buy all cans of one color at once so the shade matches.