Paint Calculator

How much paint does a room need?

Find the wall area, subtract the openings, then multiply by your coats and divide by the coverage on the can.

Worked example: a 15 × 12 ft room with 8 ft walls

1. Wall area: 2 × (15 + 12) × 8 = 432 sq ft.
2. Subtract one door (21 sq ft) and two windows (15 sq ft each): 432 − 51 = 381 sq ft.
3. Two coats at 350 sq ft per gallon: 381 × 2 ÷ 350 = 2.18 gallons.
4. Buy 2 gallons and 1 quart, which is 2.25 gallons.

Why results are rounded to gallons and quarts

The calculator rounds up to the next quart. If that would mean three loose quarts, it suggests another gallon instead, because a gallon usually costs about the same or less. In metric mode it picks a mix of 5 L, 2.5 L and 1 L tins. Sizes and prices vary by store, so compare before you buy.

Estimating the cost of paint

Enter the price per gallon of the paint you're considering, or the price per litre in metric mode. As an illustration only, the 2.25 gallons in this example at $40 per gallon comes to 2.25 × $40 = $90. A quart usually costs more than a quarter of a gallon, so the real total can be a little higher. Primer, rollers and tape aren't included.

When paint covers less than the can says

• Textured or porous walls: bare plaster, new drywall and heavy texture absorb more, so lower the coverage figure.
• Strong color changes: going from dark to light may take a tinted primer or an extra coat.
• Budget paints: some cover closer to 250–300 sq ft per gallon. Use the figure on the product you choose.
• Sprayers: overspray uses more paint than rolling, so plan on some extra.

Trim and ceilings

Ceilings usually take a different paint, so they are shown as a separate item when you include them. Trim isn't included, and most rooms need only a quart. Keep a little left over for touch-ups, labeled with the room and the color name.

Hanging new walls first? The drywall calculator uses the same room measurements.