Paint calculations are straightforward once you have the right formula — but most people either over-buy or make an extra trip mid-project. This calculator handles the wall area math, subtracts doors and windows, accounts for multiple coats, and rounds appropriately.
Coverage rate changes depending on the sheen you choose — this calculator adjusts automatically. Flat/matte covers about 400 sq ft per gallon. Eggshell and satin cover approximately 350 sq ft. Semi-gloss builds a thicker film and covers around 300 sq ft per gallon. Textured or porous surfaces reduce coverage further — always check your specific paint label.
For Sherwin-Williams paint lines: Emerald interior typically runs $55–$75/gallon, Duration (interior/exterior) $60–$80, and SuperPaint $45–$55. Prices vary — check your local Sherwin-Williams store for current pricing.
Buy the extra quart: We round up so you have touch-up paint for the inevitable nick three months later. Write the color code on the lid before you store it.
A gallon of interior paint typically covers 350-400 square feet per coat on a smooth primed surface. Texture and porosity reduce coverage. Semi-gloss and gloss may cover slightly less than flat or eggshell.
Prime if making a dramatic color change, painting new drywall, covering stains, or painting over a glossy surface. Many paints marketed as paint-and-primer still benefit from a dedicated primer coat in demanding situations.
Two coats is standard. One coat may work for same-color touch-up. Three coats may be needed for dramatic color changes, stain coverage, or new drywall.
Most latex interior paints need 2-4 hours between coats at 65-85°F and 50% humidity. Check the label — recoat time varies by product.
Buy gallons for large areas — much cheaper per ounce. Buy quarts for accent walls or small rooms. Always buy an extra quart of your main wall color for touch-ups.