How much paint do I need?

Measure the paintable wall and ceiling area, then divide the coated area by the coverage printed for the exact paint being used.

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ToolPaint Calculator
Input
Output
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How it works

The four walls total 2 × (length + width) × height, after which the measured area of unpainted doors and windows is deducted. A selected ceiling adds length × width; multiplying by the required coats and dividing by the label coverage gives litres rather than an invented tin count.

Formula
litres = (paintable area × coats) ÷ label coverage in m²/L
  • Coverage and coat count are mandatory because Dulux states that both vary by product and surface.
  • Opening area defaults to zero and ceiling area is excluded until selected, so neither surface assumption changes the estimate silently.

Worked example

A bedroom in two coats
4m by 3m, 2.4m high, one door and one window
Input
											Length m: 4
Width m: 3
Height m: 2.4
Opening area m2: 3
Coats: 2
Coverage m2 per litre: 14
Output
												Wall area: 30.6
Ceiling area: 12
Litres needed: 4.37
Deducted area: 3

When to use this

Bedroom and living-room estimates total four walls, rental redecorating deducts measured openings, and ceiling projects add the room footprint with the ceiling paint’s own coverage.

Edge cases

  • An opening total equal to or larger than all four walls is rejected rather than producing a zero or negative paintable area.
  • A one-coat product must be entered as one coat and a conventional two-coat emulsion as two; no universal count is supplied.
  • A porous wall or lower-coverage finish must use its own tin value because one fixed m²/L rate cannot represent every paint and substrate.

References