Paint Coverage Calculator — How Far Does a Gallon Go?
Work out how much area your paint will cover and how many litres or gallons you need. Enter wall dimensions, pick the number of coats, and get the amount to buy with sensible can sizes — no half-used tins.
How far does a gallon of paint go?
A US gallon of matte or eggshell emulsion covers roughly 400–490 sq ft in one coat — 10–12 m² per litre. Gloss and satinwood spread thinner at 325–400 sq ft/gal (8–10 m²/L), primer thinner still at 245–325 (6–8 m²/L). Two coats is normal, so halve those figures for a finished wall.
Why does the tin never cover what it claims?
The number on the label is measured on a sealed, smooth, primed surface. Bare plaster, new filler and anything textured drink the first coat — expect 20–30% less on a first coat over fresh work. Colour matters too: covering dark with light can take three coats however good the paint is.
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How paint coverage is calculated
- 1Wall area: (2 × length + 2 × width) × height
- 2Subtract doors (approx. 1.8 m² / 19 sq ft each) and windows (approx. 1.2 m² / 13 sq ft each)
- 3Add ceiling area if painting: length × width
- 4Amount needed: area ÷ spreading rate × number of coats
- 5Spreading rate varies: matte 10–12 m²/L (400–490 sq ft/gal), gloss 8–10 m²/L (325–400 sq ft/gal), primer 6–8 m²/L (245–325 sq ft/gal)
- 6Round up to the nearest can size to avoid partial-tin waste
Worked example
Bedroom: 4 × 3.5 m (13 × 11½ ft), walls 2.4 m (8 ft) high, one door and one window. Two coats of matte emulsion — 11 m²/L, or 450 sq ft per US gallon.
Wall area: 36.0 m² − 3.0 m² openings = 33.0 m², about 355 sq ft. Two coats: 66.0 m² (710 sq ft) ÷ 11 = 6.0 L. Buy two 3 L tins, or one 5 L tin plus one 1 L tin — in US sizes 1.6 gallons, so buy two.
Frequently asked questions
How much does a gallon of paint cover?
A US gallon (3.78 L) of typical wall paint covers roughly 38–45 m² (400–480 sq ft) in one coat at a 10–12 m²/L spreading rate. Always check the product data sheet — coverage varies by paint and surface.
How many m² does a litre of paint cover?
Typically 10–12 m² per litre for matte and eggshell wall paint — 400–490 sq ft per US gallon. Gloss and satinwood cover 8–10 m²/L (325–400 sq ft/gal). Primer covers 6–8 m²/L (245–325 sq ft/gal).
How many coats of paint do I need?
New plaster or a big colour change: 3 coats (primer + 2 top coats). Repainting a similar colour: 2 coats. Same colour refresh: 1–2 coats.
Does textured surface change paint coverage?
Yes — rough or porous surfaces (new plaster, textured render, bare wood) absorb more paint and can reduce coverage noticeably. Use primer first and expect the lower end of the spreading-rate range.