Spread rate
How far a gallon of paint goes — about 350 sq ft per coat on smooth, primed walls.
Spread rate (or 'coverage') is the area one gallon of paint covers in a single coat. The industry rule of thumb is **350 square feet per gallon** on smooth, sealed, primed drywall — which is what the [paint calculator](/guides/how-much-paint-do-i-need-calculator) assumes. Real-world coverage drops fast on anything that drinks paint or adds surface area: textured or 'orange-peel' walls, raw drywall, fresh patches, and porous masonry can pull a gallon down to 200–250 sq ft. Deep or bright colors going over a light wall often need an extra coat to hide, which effectively cuts the spread rate too. Always check the spread rate printed on your specific can — premium paints with more solids cover more per coat — and round up when you buy.