How to paint a room: quantities, order of work and drying times

1. Measure and make the shopping list

Measure the room’s length, width and wall height, and count the doors and windows. For the 12 × 12 example that is 384 sq ft of wall, 334 after a door and two windows, and a 144 sq ft ceiling.

Bigger and smaller rooms scale the same way: how much paint for a 12x14 room tips just past two gallons, and a small bathroom is a single gallon once the tile is taken out. If your paint is sold in litres, how many litres of paint for a 10x12 room shows the same math in tins.

2. Prepare the room

• Move furniture to the middle and cover it; cover the floor with canvas drop cloths.
• Take off switch plates, outlet covers, curtain rods and picture hooks.
• Wash greasy or dirty areas (kitchens, around switches) with a mild cleaner and rinse; paint doesn’t stick to grime.
• Fill holes and dings with spackle, let them dry, sand flush, and wipe off the dust.
• Caulk gaps between trim and wall and along the top of baseboards; let the caulk reach its paint-ready time.
• Scuff-sand glossy trim so the new paint grips.

3. Prime where it’s needed

New drywall, patches, stains, bare wood and glossy surfaces need primer, and so does a big color change: going from a dark color to a light one, a coat of tinted primer over the whole wall usually saves a finish coat (the primer calculator has a color-change option). Sound painted walls getting a similar color usually don’t. Spot-prime patches so they don’t flash through the finish. The data sheets for the ProMar 200 line, for example, specify one coat of primer and two finish coats on new drywall.

4. Paint the ceiling first

Cut in a 2–3 in band along the top of every wall with a brush, then roll the ceiling while the band is still wet, in strips across the room’s short direction. Work toward the main window and finish each strip in one direction so the roller marks line up with the light. Ceiling paint is flat and formulated to spatter less.

5. Then the walls

• Cut in along the ceiling line, corners, baseboards and casings, one wall at a time, so the cut band is still wet when you roll next to it.
• Roll in sections about 3 ft wide, top to bottom, keeping a wet edge. Load the roller evenly and don’t try to stretch the paint: the coverage on the can assumes the full film thickness.
• Second coat after the recoat time on the can (four hours on the ProMar 200 sheets at 77°F and 50% humidity; longer when it is cool or humid).
• Accent wall? Paint the lighter walls first, then tape and paint the accent; see how much paint for an accent wall.

6. Finish with the trim

Paint baseboards, casings and doors last, with an enamel in satin or semi-gloss and a good angled brush. If you prefer, tape the wall side of the trim once the walls are dry. One door, both sides and edges, is about three-quarters of a quart for two coats: how much paint for a door.

7. Clean up and keep the leftovers

• Pull tape at an angle once the last coat is dry to the touch, before it fully cures.
• Wash latex brushes and rollers in water; dispose of rinse water and leftover paint as your local rules say.
• Label a small container of each color with the room, product, sheen and color formula for touch-ups.
• Keep the room ventilated for a day or two. Behr’s data sheets note that most emissions occur during painting and for 48 hours after, and some continue for two weeks or longer.

How long it takes

For one person, a bedroom like this is typically a weekend: a day of moving, patching, caulking and taping, then the ceiling and first wall coat, and the second coat and trim the next day. Drying times on the can set the pace more than your speed does; plan for them rather than rushing a coat onto tacky paint.