How much does a gallon of paint cover?

About 350–400 square feet per coat, according to Sherwin-Williams — about 8.6–9.8 m² per litre. The can's own figure is the one to use, and rough or porous surfaces get less.

How much paint do I need for a 12 × 12 room?

With 8 ft walls, four walls are 4 × 12 × 8 = 384 sq ft. Two coats at 400 sq ft a gallon is 1.92 gallons, so 2 gallons; add the ceiling (144 sq ft, two coats = 0.72 gallon) and it is 3.

How many coats of paint do I need?

Two is the usual answer for a colour change; a fresh coat of the same colour over sound paint can need one. Big colour changes and bare surfaces may need a primer plus two.

How do I convert square feet per gallon to square metres per litre?

Divide by 40.7. 400 sq ft a gallon ÷ 40.7 = 9.8 m² a litre; 350 sq ft a gallon is 8.6 m² a litre.

Paint Calculator: How Much Paint for a Room

Litres or gallons of paint from the wall area, the number of coats and the can's coverage.

Inputs

Surface area(m²)

0.1 m²10,000 m²

Coverage per litre(m²/L)

1 m²/L30 m²/L

From the can. Sherwin-Williams puts a typical gallon at 350–400 sq ft, which is 8.6–9.8 m² a litre.

Number of coats

Extra for touch-ups and texture(%)

0 %50 %

Units

Include CalculateEveryday mark

Paint needed

9 L

Working: 40 m² × 2 coats ÷ 9.8 m² a litre = 8.16 L, + 10% = 8.98 L
Wall area: 40 m²
Coats: 2
Without waste: 8.2 L

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What each Paint input means

Surface area: The area to paint, in m² or sq ft: each wall's width × height, added up, less any large doors and windows. For a ceiling, the room's length × width.
Coverage per litre: What the paint covers per litre, or per gallon in US units, from the can's label. Sherwin-Williams gives about 350–400 sq ft a gallon (8.6–9.8 m² a litre) as typical; use the low end for rough or porous walls.
Number of coats: How many coats. Every coat covers the whole area again, so two coats need twice the paint.
Extra for touch-ups and texture: Extra for the tray, the roller and touch-ups later; 10% is a common allowance.
Units: Metric (metres, m², litres) or US units (feet, square feet, gallons). The wall area and coverage switch with it, so a can's sq ft per gallon figure can go straight in.

Paint formula

paint = area × coats ÷ coverage per litre (or gallon) × (1 + extra %)

P = \frac{A \times c}{k} \times \left(1 + \frac{p}{100}\right)

Sherwin-Williams' own method is to measure the area to be painted, find how much area one gallon of the chosen product covers, and divide. Every coat paints the whole area again, so multiply the area by the number of coats first. A gallon typically covers 350–400 square feet, which is 8.6–9.8 square metres a litre; the can's label gives the figure for that product. Rough, porous or textured walls — new plaster, bare masonry, popcorn ceilings — soak up more, so the real coverage is lower and a little extra on hand is sensible. Measure each wall as width × height, add them, and take off doors and windows if they are large.

Paint worked example

A room with 40 m² of wall, two coats: 40 × 2 = 80 m² of painting. At 9.8 m² a litre that is 8.2 L, and with 10% extra for touch-ups about 9 L. In US units the same room is 431 sq ft of wall; two coats at 400 sq ft a gallon is 2.15 gallons, 2.37 with the extra — so 3 gallon cans.

More Paint examples

A 12 × 12 ft bedroom with 8 ft walls has 4 × 12 × 8 = 384 sq ft of wall. Two coats at 400 sq ft a gallon is 1.92 gallons, 2.11 gal with 10% extra — so three gallon cans, or a gallon and a two-gallon size if the store sells one.

A living room with 55 m² of wall in a paint that covers 9 m² a litre, two coats: 55 × 2 ÷ 9 = 12.22 L, and 13.4 L with 10% extra — for example a 10 L tin and a 5 L tin.

Where the Paint calculator can give the wrong answer

A dark colour over a light one, or a light over dark, can need a third coat; a primer coat is often a different product with its own coverage, so work it out separately.
Bare plaster and masonry drink paint. Use the lower end of the can's range, or a primer first.
Ceilings are their own area: length × width of the room.
Doors and windows only matter when they are big: an 80 × 36 inch door is 20 sq ft (1.9 m²) that needs no paint.

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Paint reference table

Paint for common room sizes: 8 ft walls, two coats, 400 sq ft a gallon, before extra
Room	Wall area	Walls, gallons	Ceiling area	Ceiling, gallons
10 × 10 ft	320 sq ft	1.6	100 sq ft	0.5
12 × 12 ft	384 sq ft	1.92	144 sq ft	0.72
12 × 14 ft	416 sq ft	2.08	168 sq ft	0.84
14 × 16 ft	480 sq ft	2.4	224 sq ft	1.12
16 × 20 ft	576 sq ft	2.88	320 sq ft	1.6

Source: Arithmetic: walls = 2 × (length + width) × 8 ft; gallons = area × 2 coats ÷ 400, the top of Sherwin-Williams' 350–400 sq ft range; doors and windows not subtracted

Paint FAQ

: About 350–400 square feet per coat, according to Sherwin-Williams — about 8.6–9.8 m² per litre. The can's own figure is the one to use, and rough or porous surfaces get less.
: With 8 ft walls, four walls are 4 × 12 × 8 = 384 sq ft. Two coats at 400 sq ft a gallon is 1.92 gallons, so 2 gallons; add the ceiling (144 sq ft, two coats = 0.72 gallon) and it is 3.
: Two is the usual answer for a colour change; a fresh coat of the same colour over sound paint can need one. Big colour changes and bare surfaces may need a primer plus two.
: Divide by 40.7. 400 sq ft a gallon ÷ 40.7 = 9.8 m² a litre; 350 sq ft a gallon is 8.6 m² a litre.