How to paint a room: a 12 by 14 bedroom, step by step, with the paint math

How much paint do you need for a room?

Wall area minus openings, times coats, divided by coverage: this bedroom needs 1.86 gallons for two coats, so you buy two gallons. The bedroom is 12 by 14 ft with 8 ft ceilings. Walls: 2 × (12 + 14) × 8 = 416 sq ft. Openings are measured, not guessed: a 36 by 80 inch door is 20 sq ft and two 36 by 48 inch windows are 24 sq ft, so 372 sq ft gets paint. The ceiling adds 168 sq ft if you do it, and usually takes a separate flat ceiling white.

Coverage is the manufacturer's: Benjamin Moore rates Regal Select eggshell at 400 to 450 sq ft per gallon. I use 400. Walls have outlets, corners and the thick band you cut in with a brush, and the lab number assumes none of that. Put the same inputs in the paint calculator (walls already painted, same color, coverage 400) and it returns the same result as the table below, because the table was computed with the calculator's own code.

The last two rows are the decision that matters. Covering a dark wall in a light color with paint alone takes 4 coats by the calculator's rule of thumb. A gallon of Fresh Start primer ($54.99) plus 2 coats costs $114.99 less and saves two rounds of cutting in. Tint the primer toward the new color, as Benjamin Moore's data sheets advise.

What paint finish to use in each room, including the bathroom

Eggshell for a bedroom, satin or semi-gloss for trim and doors, flat for the ceiling, and a humidity-rated paint in the bathroom. Flat and matte hide wall flaws and touch up invisibly; higher sheens wipe clean and show every dent. For a bedroom, eggshell is the usual compromise, and Regal Select's specs list scuff resistance and a mildew resistant coating. Trim and doors get satin or semi-gloss enamel. Ceilings get flat.

Bathrooms are the exception, and the answer to "best paint for the bathroom" is a humidity-rated product more than a sheen. Benjamin Moore's Aura Bath & Spa is a matte paint with a mildew and mold resistant coating, rated scrubbable, 350 to 400 sq ft per gallon, recoat in 1 hour. The manufacturer's own answers on its page set the limits: not on shower walls that get wet, a satin like Kitchen & Bath where water splashes the wall often, and run the exhaust fan during and after showers. Sherwin-Williams adds the step people skip: mildew has to be removed before painting, or it grows through the new coat.

The bathroom case: 5 by 8 ft, 8 ft ceiling, a 30 by 80 inch door and a tiled tub surround covering 60 sq ft of wall. That leaves 131 sq ft of wall and 40 of ceiling. Two coats at 350 sq ft per gallon come to 0.98 gallon. The calculator treats walls and ceiling as separate paints, so it returns one gallon plus one quart, $155.98. If the same paint goes on both, one $108.99 gallon covers it with 0.02 gallon to spare, which is nothing. Buy the quart anyway; bathrooms need touch-ups.

What you need to paint a room

Paint, an angled brush, a roller with 3/8 in covers, a tray, tape, patching supplies and a drop cloth: $241.49 for this bedroom, $169.98 of it paint.

One 60-yard roll of tape is 180 ft. The baseboard, door casing and two window casings in this room come to roughly 95 ft of edge, so one roll covers it even if you tape the ceiling line too.

Also needed and probably already in the garage: a stepladder, a screwdriver for outlet covers, a bucket and sponge, a putty knife, rags. Worth having: an extension pole for the roller, which saves your shoulders on the upper half of every wall. Luxury: a paint sprayer. On one bedroom the masking takes longer than the rolling it replaces.

How to paint a room, step by step

1. Check the house's age before you sand anything. In a home built before 1978 the old paint may contain lead. EPA's RRP rule binds anyone you pay to disturb it; it generally does not bind you in your own home, but EPA recommends testing by a certified inspector and lead-safe practices such as misting before sanding. The minor-repair exception is 6 sq ft of interior surface. Check: tested, or you are only washing and spot-filling, not sanding whole walls.
2. Empty the room or pull furniture to the center and cover it. Remove outlet and switch covers and put the screws back in their plates. Drop cloth along the wall you are working on. Check: nothing within 3 ft of a wall, and the floor edge is covered.
3. Wash the walls with mild detergent and rinse, with extra attention around switches and the headboard wall. Remove any mildew first. Check: a damp white rag comes off the wall clean.
4. Fill nail holes and dents with spackling, let it dry, sand flush with the sponge. Caulk open gaps between the trim and the wall. Glossy old paint should be dulled, per Benjamin Moore. Check: running a hand over the patches, you cannot find them with your eyes closed.
5. Tape the baseboards and casings, pressing the edge down with a putty knife. Skip taping the ceiling line if you have a steady hand; tape it if the ceiling is a different color. Check: no gaps under the tape edge when you look along it.
6. Prime if you are covering a dark color, patches larger than your hand, or bare drywall. Check: the patches no longer look dull or chalky compared with the wall around them.
7. Cut in. Load the angle brush a third of the bristle length, and paint a band about 2 to 3 inches wide along the ceiling, the corners, the trim and around the outlets. Do one wall's edges, then roll that wall while the band is still wet. Check: the band has a feathered edge, not a hard ridge of paint.
8. Roll. Load the roller evenly on the tray, start about a foot from a corner, roll a wide W or N shape of roughly 3 by 3 ft, then fill it in without lifting, and finish with light vertical strokes top to bottom. Work toward the wet paint, never back into paint that has started to set; Benjamin Moore's instruction is to maintain a wet edge to avoid lap marks. Check: look at the wall at a low angle toward the window; no shiny stripes where one section overlapped another after drying.
9. Wait out the recoat time: 1 to 2 hours for Regal Select by Benjamin Moore's spec, longer if the room is cool or humid. Then repeat the cutting in and rolling. Check: the first coat is dry to the touch in the brush band, which is always the last place to dry.
10. Pull the tape while the second coat is still slightly soft, at a low angle away from the fresh paint. Check: a clean line, with no paint peeling off the wall along with the tape.
11. Clean the brush and roller with warm soapy water, put the covers and furniture back after the paint is dry to the touch, and keep furniture a few inches off the walls for a couple of days. Check: no marks on the walls from the backs of furniture the next day.

Mistakes that cost money

Buying by the quart. The bedroom needs 1.86 gallons. One gallon and four quarts cost $224.95; two gallons cost $169.98. The quart route costs $54.97 more and gives you the same paint.

Covering a dark color with paint alone. Four coats of Regal Select is $339.96 and two extra days of cutting in. Primer plus two coats is $224.97. The difference is $114.99, and the primer coat also hides patches that paint alone would flash through.

Using wall paint in a bathroom without a fan, or skipping the mildew wash. Mildew comes back through the new coat and the room gets repainted: another $108.99 gallon of bathroom paint plus the prep.

Rolling over a half-dry edge. Lap marks do not sand out. The fix is another full coat on that wall: 96 sq ft on the plain 12 ft wall of this room, or roughly a quarter gallon and an evening.

Painting over glossy enamel without dulling it. Benjamin Moore's data sheets say glossy areas should be dulled, and a coat that cannot grip will lift when tape or a picture hanger pulls on it. The fix is scraping, sanding and repainting that wall, all to save a $2.49 sanding sponge and an hour.

How much does it cost to paint a room?

About $241 in materials if you paint this 12 by 14 bedroom yourself, or $372 to $744 for a painter at This Old House's $1 to $2 per square foot of wall.

Painters earned a median of $23.75 an hour nationally in May 2025 (BLS OEWS, occupation 47-2141). Divided by 0.695, since wages are 69.5% of total compensation in private construction, the employer's cost is $34.17 an hour before overhead and profit. By state the median runs from $21.86 in Texas and $22.85 in Florida to $28.38 in California and $28.64 in New York, or $31.45 to $41.21 loaded.

This Old House reports walls are usually quoted at $1 to $2 per square foot of surface, which is $372 to $744 for this room, and $300 to $800 for an average 132 sq ft bedroom. It also reports labor rates of $30 to $60 an hour, which lines up with the $31 to $41 loaded wage above plus a margin. A painter's quote includes the paint, so the saving from doing it yourself is the quote minus your $241:

At the low end you are working for $13 an hour, and a pro will be faster and cleaner. At the midpoint you earn about what the painter's employer pays for the painter. A light-over-dark job, a 9 ft ceiling or a bathroom full of fixtures pushes the quote up faster than your costs, and that is where DIY pays best. The tools stay with you, and the second room costs about $170 in paint and very little else.

Patching drywall first? The drywall calculator covers board, mud and tape, and the paint calculator handles several rooms at once. Doing the kitchen next? The guide on how to paint kitchen cabinets covers the bonding primer and enamel that cabinets need, and the one on how to hang wallpaper counts rolls for this same bedroom.