Paint Calculator

Please fill in the required fields with values greater than 0.
–sq ft of wall to paint (one coat)
–gallons for walls
–1-gallon cans
–gallons for ceiling

Estimate only. Coverage depends on the paint, the surface and how it is applied, so check the label. Buy a little extra for touch-ups.

How to use this calculator

Enter the room length, width and ceiling height, then the number of doors and windows. Choose the number of coats and press Calculate. You get the wall area, the gallons of wall paint and the gallons for the ceiling.

The formula

Wall area = 2 × (length + width) × height − doors (20 sq ft each) − windows (15 sq ft each)
Gallons = wall area × coats ÷ coverage per gallon (about 350 sq ft)

Example: A 12 ft × 10 ft room with 8 ft walls, 1 door and 2 windows has 302 sq ft of wall. Two coats need about 1.73 gallons, so buy 2 one-gallon cans. The ceiling needs about 0.69 gallons for two coats.

Understanding your paint estimate

The paint calculator gives you the wall area to paint, the gallons needed for the walls and the gallons needed for the ceiling. The gallon figures already include the number of coats you chose. Round them up to whole cans, since you cannot buy 1.73 gallons.

What changes how much paint you need

  • Wall height. Taller walls add area fast. A 9 foot wall has 12.5% more area than an 8 foot wall.
  • Doors and windows. The tool subtracts about 20 square feet per door and 15 per window.
  • Number of coats. Two coats double the paint needed compared with one.
  • Surface and color. Rough, porous or bare surfaces soak up more paint. Big color changes may need an extra coat or primer.

Two examples

A 12 by 10 foot room with 8 foot walls, one door and two windows has about 302 square feet of wall. Two coats at 350 square feet per gallon need about 1.73 gallons, so buy two gallons. The ceiling needs about 0.69 gallon for two coats.

A larger 14 by 12 foot room with 9 foot walls has 2 × 26 × 9 = 468 square feet before openings. With one door and two windows, that drops to 418 square feet. Two coats need about 2.39 gallons, so plan on three gallons. The ceiling needs almost one gallon.

Tips and common mistakes

  • Check the coverage on the can. Some paints cover less than 350 square feet per gallon.
  • Count trim and doors separately. They usually take a different sheen, such as semi-gloss.
  • Do not skip primer on new drywall, stains or glossy surfaces. Paint alone may not stick or hide well.
  • Mix all cans together in a larger bucket for even color across walls.
  • Buy tape, drop cloths and rollers with the paint. A good roller cover spreads paint more evenly.

Buying and cost advice

Gallon cans are often cheaper per gallon in a 5 gallon bucket if you need four or more. Keep the receipt and ask about the return policy on unopened cans. Higher quality paint usually covers better, which can save a coat. Label any leftover can with the room name and color code for future touch-ups.

Frequently asked questions

How much paint do I need for a room?
Multiply the wall area by the number of coats and divide by the coverage per gallon, which is about 350 square feet. Subtract doors and windows first.
How many coats of paint should I use?
Two coats give the best finish and color for most walls. Use a primer if you are covering a dark color or bare drywall.
How much does a gallon of paint cover?
About 350 to 400 square feet for one coat.
Should I paint the ceiling too?
Ceilings are usually painted with a separate flat white paint. Use the ceiling result above to buy the right amount.
How much extra paint should I buy?
Buy about 10 percent extra for touch-ups and uneven walls.
How long should paint dry between coats?
Most interior latex paints are dry to the touch in about an hour and ready for a second coat in about 2 to 4 hours. Oil-based paints usually need much longer, often a full day. Cool or humid weather slows drying. Always follow the recoat time printed on the can.
What paint finish is best for walls?
Eggshell and satin are popular for most rooms because they are easy to clean and hide minor flaws. Flat or matte hides imperfections best but marks more easily. Semi-gloss is common for trim, doors, kitchens and bathrooms because it stands up to moisture and scrubbing.
Do I need primer before painting?
Use primer on new drywall, bare wood, patched spots, stains and glossy surfaces. It helps paint stick and gives an even finish. When repainting a clean wall in a similar color, a quality paint-and-primer product or two coats of paint is usually enough. Dark-to-light changes often benefit from a tinted primer.