Paint Calculator
Find out exactly how many gallons of paint your room or house needs.
About the Paint Calculator
Buying too little paint forces a mid-project trip to the store — and risks color-matching issues if you need a second can mixed separately. Buying too much wastes money. This Paint Calculator finds the just-right amount.
How Coverage Is Calculated
Total paintable wall area = Room perimeter × Wall height, minus door and window openings. One standard door = approx. 20 sq ft. One standard window = approx. 15 sq ft. Then divide by the paint's coverage rate (typically 350–400 sq ft per gallon), and multiply by the number of coats.
Coverage Rates by Paint Type
Primer: 200–300 sq ft/gallon (goes on thicker) | Flat/matte interior: 350–400 sq ft/gallon | Eggshell/satin: 350–400 sq ft/gallon | Semi-gloss/gloss: 400 sq ft/gallon | Exterior paint: 300–400 sq ft/gallon (rough surfaces absorb more)
How Many Coats Do You Need?
Self-priming paint over same or similar color: 1 coat may suffice. Drastic color change (dark to light or vice versa): Primer + 2 coats. New drywall: Always prime first, then 2 finish coats. High-moisture areas (bathroom, kitchen): 2 coats of moisture-resistant paint.
Ceiling Paint
This calculator covers walls only. For ceilings, multiply room length by width. A ceiling is typically only one coat unless you're making a major color change. Use a flat or matte ceiling paint for best results (it hides imperfections).
Leftover Paint Storage
Store unused paint tightly sealed in a temperature-controlled area (40–80°F). Use a rubber mallet to seat the lid firmly. Properly stored latex paint lasts 2–5 years. Label each can with the color name, room painted, and date.