Paint Calculator & Room Painting Planner

A 12 × 12 room with 8 ft ceilings has about 384 sq ft of wall, minus roughly 51 sq ft for a door and two windows. Two coats at 350 sq ft per gallon works out to just under two gallons. This planner does that arithmetic with your actual numbers.

Almost always. One coat only looks right when you are repainting the same colour on a wall in good condition. Colour changes, fresh drywall, and any patching all show through a single coat.

Prime bare drywall, patched areas, stains, glossy surfaces, and dramatic colour changes. Repainting a similar colour over sound paint generally does not need it — a paint-and-primer product is fine there.

Coverage figures assume a smooth, primed, similar-coloured surface. Texture, porosity, and colour change all cut real coverage — sometimes by a third. If your walls are textured, increase coverage expectations accordingly.