How to paint a room: prep, coats and cleanup
Clear and protect the room, clean and patch the walls, prime what needs it, then paint the ceiling first, the walls next and the trim last, waiting the can’s recoat time between coats.
In a house built before 1978 the old paint may contain lead: test it before you sand or scrape. Fix the cause of a damp patch before painting over it, because paint will not stop a leak.
Worked example
Example: a 12 × 10 ft room with 8 ft walls, one door and two windows (38 sq ft), two coats and 400 sq ft per gallon.
This example gives 2 1-gallon paint cans.
- Surface area: 314 sq ft
- ceil(314 × 2 × (1 + 0/100) ÷ 400) = 2
Other calculators for this job
Every step of a paint and drywall project: measure, the list, what it costs and the quotes.
Work out what you need
Measure walls, ceiling, doors and trim separately and write the color and finish beside each. The paint calculator turns the room into cans: Sherwin-Williams puts a gallon at up to 400 sq ft per coat on a smooth wall, and rough or porous walls take more. A color change or new patches usually take two coats. Buy each color at once, or pour its cans together before you start, so the shade matches across the wall.
Clear and protect the room
Move furniture to the middle and cover it, lay drop cloths and take off switch plates and outlet covers. Mask any edge you cannot cut in neatly. Sherwin-Williams’ How to Prep Walls for Painting lists the same order before paint: protect the room, clean, patch, caulk and prime.
Clean, patch and sand
Wash greasy or grubby areas, such as kitchen walls and around switches, and let them dry. Scrape loose paint, fill holes and cracks, sand the patches smooth once dry and caulk gaps along the trim. Sherwin-Williams’ preparation guidance warns about the dust from disturbing old paint, which is where the lead test comes in.
Prime what needs it
Prime bare drywall, patches, stains and glossy surfaces, and use a stain-blocking primer over water marks or smoke. A big color change goes faster over a tinted primer. Use the primer the paint maker names for your surface; the calculator lists primer on its own line so you buy the right amount.
Paint in order: ceiling, walls, trim
Cut in a band with a brush along the ceiling, corners and trim, then roll that wall while the band is still wet so the two blend. Work from the top down: ceiling first, walls next, trim and doors last. Wait the recoat time on the can before the second coat; water-based paint is often ready in a few hours, but the label decides. Keep a window open while you work.
Finish and clean up
Pull the tape soon after the last coat, while the paint is still soft, so it leaves a clean edge. Check the walls in daylight once dry and touch up thin spots. Rinse water-based paint out of brushes and rollers with water. Dry to the touch is not fully cured, so go gently with washing for the first weeks, and keep the paint name, color and finish for touch-ups. A painter’s quote should list prep, protection, coats, repairs and cleanup, not just a price per room.