Home › Construction & Trade Calculators › Paint
🎨 Construction & Trade Calculators
Free Paint Calculator — How Many Gallons Do I Need?
Estimate the number of paint gallons needed for your project. Add multiple wall surfaces, subtract doors, windows, and other openings, then adjust for your paint's coverage rate and number of coats. The calculator shows gallons needed and rounds up to the next full gallon to buy.
Frequently asked questions
How much paint do I need for a 12x12 room?
A 12×12 room with 8-foot ceilings has approximately 384 sq ft of wall area. Subtracting a door and window (~60 sq ft), you need about 324 sq ft of coverage. At 350 sq ft/gallon, that's about 1 gallon per coat.
How many square feet does a gallon of paint cover?
Most interior paints cover 350–400 square feet per gallon on smooth surfaces. Rough or porous surfaces may require more paint. Always check your specific paint's coverage rate.
Related tools