Paint Calculators

Paint is sold by the gallon and covers a set area, so the quantity comes from the wall area, the openings you subtract and the number of coats. The tools here work that out and add a cost estimate, and the can's label has the exact coverage.

Which tool answers which question

• Exterior Paint Cost Calculator: Estimate gallons and the cost to paint your house exterior by size, stories and siding type.
• Interior Paint Cost Calculator: Compare the cost of painting rooms yourself with hiring a pro, using editable paint and labor prices.
• Paint Calculator: Enter room size, doors, windows and coats to get wall area, gallons and cans of paint to buy.
• Paint Coverage Calculator: Convert gallons to square feet, or square feet to gallons, adjusted for coats and surface texture.

Coverage, coats and primer

Most paint covers about 350 to 400 square feet per gallon on smooth, primed walls, and less on rough or porous surfaces. Two coats are common, and a new drywall or a big color change usually needs primer first. Buy a little extra for touch-ups and keep a record of the color.

Older homes

Houses built before 1978 may have lead-based paint. Do not sand or scrape suspect paint without testing and following lead-safe work practices, and use a certified professional if the rules require one.

Common mistakes

• Forgetting the second coat. Coverage figures are per coat.
• Skipping primer. It saves paint on bare or patched surfaces.
• Sanding old paint dry. Test for lead first in older homes.
• Using different batches. Mix cans together to even out color.