Most bedrooms need about 2 gallons of paint for two coats on the walls. The math is square feet × coats ÷ coverage per gallon. A 12 × 14 ft room with 8 ft ceilings has about 365 sq ft of paintable wall once you take off a door and two windows, and 365 × 2 ÷ 400 = 1.8 gallons. Round up to 2.
There are only three numbers in the whole calculation: the area you're painting, the number of coats, and how far one gallon spreads.
Gallons = square feet × coats ÷ coverage per gallon
Then round up to what the store actually sells. That's the same formula our paint calculator runs, and it's worth knowing by hand because the inputs are where people go wrong, not the math.
So you buy 2 gallons and have a little left for touch-ups.
Here's the formula run for common bedroom and living room sizes. It assumes 8 ft ceilings, one door, a sensible number of windows, two coats and 400 sq ft per gallon, which is the default in the calculator.
| Room size | Wall area (8 ft) | Doors / windows | Paintable area | Gallons for 2 coats | What to buy |
|---|---|---|---|---|---|
| 10 × 10 ft | 320 sq ft | 1 / 1 | 284 sq ft | 1.42 | 1 gallon + 2 quarts, or 2 gallons |
| 10 × 12 ft | 352 sq ft | 1 / 1 | 316 sq ft | 1.58 | 2 gallons |
| 12 × 12 ft | 384 sq ft | 1 / 2 | 333 sq ft | 1.67 | 2 gallons |
| 12 × 14 ft | 416 sq ft | 1 / 2 | 365 sq ft | 1.82 | 2 gallons |
| 14 × 16 ft | 480 sq ft | 1 / 2 | 429 sq ft | 2.15 | 2 gallons + 1 quart |
| 16 × 20 ft | 576 sq ft | 1 / 3 | 510 sq ft | 2.55 | 3 gallons |
Most bedrooms need exactly 2 gallons, which is why the paint desk usually suggests it. But a 14 × 16 room tips just over the line, so check your own numbers.
Taller ceilings add up fast. The same 12 × 14 room with 9 ft ceilings has 417 sq ft of paintable wall, which needs 2.08 gallons for two coats. That's 2 gallons plus a quart, not 2 gallons.
Most interior paint cans quote somewhere between 250 and 400 sq ft per gallon. The top of that range assumes smooth, primed, previously painted drywall and a decent roller. Real walls often come in lower.
Here's how much the coverage rate changes the answer for a single room with 400 sq ft of paintable wall and two coats.
| Coverage per gallon | Typical surface | Gallons needed | Buy |
|---|---|---|---|
| 400 sq ft | Smooth, painted, same color | 2.00 | 2 gallons |
| 350 sq ft | Smooth, slight color change | 2.29 | 2 gallons + 1 quart |
| 300 sq ft | Light texture | 2.67 | 3 gallons |
| 250 sq ft | Heavy texture or porous | 3.20 | 3 gallons + 1 quart |
That's a 60% swing in paint from the wall surface alone. If you're not sure, use 350 in the calculator. It's a safer middle number than the label's best case.
Plan on two. One coat can work when you're repainting the same color, or a very close shade, over a clean wall in good shape. Everything else needs two for even color and sheen: a noticeable color change, patched spots, or a flat paint going over an eggshell.
Big jumps are harder. Covering a dark red or navy with a light color can take a primer coat plus two topcoats. A tinted primer, close to the new color, usually saves you a third coat. The calculator has a separate primer line for this, since primer is cheaper per gallon and you don't want to price it as paint.
Enter square footage, coats and coverage, add primer if you need it, and see the cost. Free, no signup.
Open the Paint Calculator →Ceilings are easier to measure: it's just length times width. A 12 × 14 ceiling is 168 sq ft, so two coats at 400 sq ft per gallon come to 0.84 gallons, or one gallon.
| Ceiling size | Area | Gallons for 2 coats | Buy |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 0.50 | 2 quarts or 1 gallon |
| 12 × 12 ft | 144 sq ft | 0.72 | 1 gallon |
| 12 × 14 ft | 168 sq ft | 0.84 | 1 gallon |
| 14 × 16 ft | 224 sq ft | 1.12 | 1 gallon + 1 quart |
| 16 × 20 ft | 320 sq ft | 1.60 | 2 gallons |
Use a flat ceiling paint. It hides roller marks and small flaws better than anything with sheen, and it's usually cheaper.
A quart is a quarter of a gallon and covers about 100 sq ft at 400 sq ft per gallon. Quarts are good for trim, a small bathroom or topping up a job that's a little over a round number. They cost a lot more per ounce, though, so four quarts is almost never a better deal than one gallon.
A 5-gallon bucket covers roughly 2,000 sq ft per coat at 400 sq ft per gallon. That's a whole-house job or several rooms in one color. It's usually cheaper per gallon than singles and has one more advantage: every drop is the same batch, so there's no color shift between cans.
If you do buy several single gallons of the same color, pour them all into one big bucket and mix before you start. Painters call this boxing. It evens out tiny differences between cans, which otherwise show up as a faint line where you opened a new one.
Paint is the easy part to budget. At $40 a gallon, which is the calculator's default and a fair mid-range price, a typical 12 × 14 bedroom costs $80 for the walls. Add a gallon of ceiling paint and maybe a quart of trim paint and you're close to $125 to $150 in paint.
Rollers, brushes, tape and drop cloths can cost as much again on a first job, but they last. If you're also replacing damaged wall sections, the drywall calculator will tell you how many sheets and how much mud you need. Refinishing the floor while the room's empty? The flooring calculator does the square footage and box count.
Measure the walls, subtract doors and windows, multiply by two coats and divide by 350 to 400. Most bedrooms land at 2 gallons. Round up, box your cans together and keep a labeled jar of the leftover for touch-ups.
About 2 gallons for the walls. A 12 × 12 room with 8 ft ceilings has 384 sq ft of wall. Take off a door and two windows and you're at roughly 333 sq ft. Two coats at 400 sq ft per gallon come to 1.67 gallons, so buy 2. The ceiling needs another gallon.
Most interior paints quote 250 to 400 sq ft per gallon. You'll get close to 400 on smooth, primed walls, and 300 or less on textured or porous surfaces. If you're unsure, plan on 350.
Double the area, then divide by the coverage. For 400 sq ft of wall at 400 sq ft per gallon, one coat takes 1 gallon and two coats take 2. Most jobs need two coats for even color, especially when you're changing color.
Usually not for the walls. A gallon gives one coat on about 400 sq ft, and even a small 10 × 10 bedroom has about 284 sq ft of paintable wall, which needs about 1.4 gallons for two coats. One gallon is often enough for the ceiling, though.
Yes, for anything bigger than a closet. Allow about 21 sq ft per standard door and 15 sq ft per window. Skip small items like outlets and switches, since they make no real difference.