Paint Coverage Calculator (Gallons and Litres)

Net wall area is 2(L+W)H minus 20 ft² (about 1.9 m²) per door and 15 ft² (about 1.4 m²) per window. Amount = area × coats / coverage. Walls only.

Inputs

Units

Results

Net wall area: 302.0ft²
Paint / stain: 1.73gal

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

Product links are Affiliate Links to Amazon websites. Using them does not cost you anything extra, and if you make a purchase we may receive a commission. Details: Terms of Service, point 5.

Calculation method

Paint = net wall area × coats ÷ coverage. A 12×10 ft room, 8 ft high, with one door and two windows has 352 − 20 − 30 = 302 ft² of wall; two coats at 350 ft²/gal need 604 ÷ 350 ≈ 1.73 gal (about 6.5 L). In metric mode coverage is entered in m²/L, the unit printed on European cans: a 4 × 3 m room, 2.5 m high, with one door and one window has about 31.7 m² of wall, and two coats at 10 m²/L need about 6.3 L.

Exact formula

Default coverage 350 ft²/gal (about 8.6 m²/L). Two finish coats are typical; new drywall is primed first.

New drywall

Prime first, then two finish coats. Budget more than a repaint on already sealed walls.

Frequently asked questions

Do I paint the ceiling here?

No. This is walls only. For a ceiling, work out L × W × coats ÷ coverage separately; ceiling paint often has its own coverage.

Primer?

Run primer as its own calculation with one coat and the primer’s coverage. Adding a coat here only works if the primer spreads like the paint.

Why is stain using the same form?

Stain is still area × coats ÷ coverage. Put the stain’s coverage in the box; rough or weathered wood can take about twice as much as smooth wood.

How many cans should I buy?

Round the result up to the sizes on sale: a US gallon is 3.79 L and a quart is a quarter of that; European cans are usually 1, 2.5, 5 or 10 L. A little left over from the same batch is handy for touch-ups.