Paint estimator

Enter the room size and the openings to skip. The estimator works out net wall area, then litres and cans from your coats and the coverage on your paint can. Inputs are metric, and results show imperial equivalents.

Estimator

Room length (m)

Room width (m)

Wall height (m)

Doors not painted

Windows not painted

Coats

Coverage per litre (sq m per L, from your can)

Can size (L)

Formula: gross wall area = 2 x (length + width) x height. Deductions stated: a standard door counts as 1.89 sq m and a typical window as 1.80 sq m. Net area = gross minus deductions. Litres = net area x coats / coverage per litre. Cans = ceiling of (litres / can size). Ceilings are not painted; add a separate ceiling area if you plan to paint it.

Worked example: Room 4 m by 3 m, walls 2.4 m high, 1 door, 1 window, 2 coats, coverage 10 sq m per litre, can 3.78 L. Gross wall area = 2 x (4 + 3) x 2.4 = 33.60 sq m. Deductions = 1.89 for the door plus 1.80 for the window = 3.69 sq m. Net area = 29.91 sq m. Paint = 29.91 x 2 / 10 = 5.98 litres. Cans = 5.98 / 3.78 = 1.58, rounded up to 2 cans.

Estimates only. Texture, colour change, primer, and surface condition change coverage. Check the coverage rate printed on your can and verify before buying.

Frequently asked questions

What coverage rate should I enter?

Use the rate printed on your paint can. Many interior paints cover about 10 sq m per litre per coat on smooth walls. Rough or unprimed surfaces cover less.

Does this include the ceiling or primer?

No. The estimator covers walls only, after door and window deductions. Add ceiling area separately if needed, and plan primer as its own product where the surface needs it.

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