How Much Paint for a Room?

The table below gives a quick gallons figure by room size, so you can grab paint without measuring first. For your own room's exact dimensions, door and window count, and number of coats, the paint calculator computes the precise amount — this page is the quick-reference version of the same method.

Gallons of paint by room size

Figures assume an 8-ft ceiling height and no subtraction for doors or windows — a conservative (slightly generous) estimate that also covers the trim-free wall area lost to a couple of average-size openings. Rooms with unusually tall ceilings, several large windows, or an open-plan layout with fewer interior walls should use the calculator directly rather than this table.

This Old House, "How Much Paint Do I Need?", attributing the figure to Lowe's: a gallon of paint usually covers 350-400 square feet — each figure is wall (or ceiling) area divided by 350 sq ft per gallon per coat, rounded up to the next whole gallon can, since paint is sold in whole-gallon units. Two coats is the standard recommendation for full coverage and even color, especially over a different existing color; one coat is realistic only over primer or an identical existing color in good condition.

Per-item estimates

A standard interior door is roughly 20 sq ft per face. Even with both faces painted at 2 coats, that's about 80 sq ft, well under a gallon, so a quart is usually enough unless you're painting several doors from one can for color-match reasons.

Exterior walls are a different case. The wall-area arithmetic is the same, but the 350 sq ft per gallon rate used on this page is an interior, smooth-wall figure. Siding texture (stucco, shingle, board-and-batten), weathered surfaces and exterior prep change real usage enough that the paint calculator treats its own exterior results as directional only, and the same applies to any exterior figure worked out from this page. For a house exterior, use this method for a rough budget, then check the coverage printed on the exterior product you choose and confirm quantities with your paint supplier.

Taller ceilings: 2 coats on walls at 8, 9 and 10 ft

Wall area grows in direct proportion to ceiling height, so a room with 10 ft ceilings has 25% more wall than the same floor plan at 8 ft. Because paint is bought in whole gallons, that extra area sometimes fits inside the rounding and sometimes adds a can. The figures below are for walls only, 2 coats, at 350 sq ft per gallon:

A room that sits close to a whole gallon at 8 ft is the one that tips over when the ceiling goes up. Vaulted and sloped ceilings don't fit this table at all, because the end walls are partly triangular. Measure those walls separately and use the calculator.

One accent wall

Painting a single feature wall is a much smaller job than the room tables suggest. A 14 ft wall at an 8 ft ceiling is 112 sq ft. Deep accent colors usually need the full 2 coats, which makes 224 sq ft of coverage, or about 0.64 gallons at 350 sq ft per gallon. A quart covers about 87.5 sq ft, so three quarts would be enough; compare their price with a single gallon, which also leaves paint for later touch-ups.

The most common measuring mistake

The number people most often use for a room is its floor area, because that is what floor plans and listings quote. Paint goes on the walls, and wall area is usually much larger. A 12 × 12 ft bedroom has 144 sq ft of floor but 2 × (12 + 12) × 8 = 384 sq ft of wall, more than two and a half times as much. Dividing the floor area by the coverage rate would suggest less than half a gallon per coat instead of more than one. Always measure around the room, not across it: add the length of every wall, multiply by the ceiling height, and only then divide by the coverage rate. The ceiling, by contrast, is the one surface where floor area is the right number to use.

Worked example: a 12 × 14 ft room, walls and ceiling

A 12 × 14 ft living room at 8 ft ceiling height has a wall area of 2 × (12 + 14) × 8= 416 sq ft. At 2 coats, that's 832 sq ft of paint coverage needed, divided by 350 sq ft/gallon = 2.38 gallons, rounded up to 3 gallons — matching the table row above. The 12 × 14 ft ceiling is a separate 168 sq ft at 1 coat, which is 168 ÷ 350 = 0.48 gallons, rounded up to a single gallon can. Buying 3 gallons of wall color and 1 gallon of ceiling color covers the room with a small amount of leftover for touch-ups, which is the built-in effect of rounding up to whole cans rather than a separately added waste allowance.

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