Calculate exactly how much paint you need for any room — no waste, no trips back to the store.
Stop doing complex calculations by hand or searching for formulas. Paint Calculator lets you calculate exactly how much paint you need for any room — no waste, no trips back to the store in seconds with a clean, easy-to-use interface. Enter your values and get instant, accurate results along with step-by-step breakdowns where applicable.
A standard 12×12 ft room with 9 ft ceilings has about 370 sq ft of wall space after deducting a door and two windows. With 2 coats at 350 sq ft/gallon coverage, you'd need approximately 2.1 gallons — so buy 2 gallons + 1 quart. Always round up to the next container size available (quart = 0.25 gal, half-gallon = 0.5 gal).
Two coats is the professional standard for most paint jobs. One coat may suffice when: re-applying the same color, using high-quality "one-coat" paint, or touching up small areas. Two coats provide better coverage, richer color, more durability, and hide imperfections. Three coats may be needed for dramatic color changes (e.g., dark to light) or for painting over stains.
Primer is a preparatory base coat that seals the surface and improves paint adhesion. You need primer when: painting over raw drywall or plaster, making a dramatic color change, painting over stains or water damage, or painting bare wood. Modern paint+primer combos can sometimes skip a separate primer coat, but a dedicated primer gives the best results on new surfaces or dramatic color changes.