How we work it out
Wall area is the room's perimeter times the wall height: 2 × (length + width) × height. Add the ceiling's own length × width if you're doing that too. Divide the total by 16, the manufacturer-stated coverage for a litre of standard interior wall or ceiling paint per coat, per Dulux's own paint calculator, then multiply by however many coats you're doing. Two coats is the standard for any real colour change; one coat only stretches far enough for a touch-up in the exact same colour, and bare plaster or a big jump in colour (dark to light or vice versa) usually wants a third.
Worked example: a 4 m × 6 m lounge room at the standard 2.4 m ceiling height has 48 m² of wall. Two coats needs 6 L, roughly $42 to $60 in a budget line or $114 to $162 in a mainstream premium brand like Dulux Wash&Wear. Doing the 24 m² ceiling as well adds another 3 L on top.
Select the third coats option (bare plaster or a big colour jump) and the docket also totals what a primer instead of a third topcoat would cost, for comparison. On Australian retail prices it's usually the pricier route, not the cheaper one, see how many coats of paint do you actually need for the full sourced breakdown.
Budget or premium?
Budget interior paint (Bunnings' own house brands are the common example) covers the same wall for a good deal less per litre, and for a rental or a low-traffic spare room it does the job. Premium tins from Dulux or Taubmans go on with fewer visible roller marks, wash cleaner, and hold their colour and sheen longer in high-traffic rooms and kitchens, which is where the extra cost tends to earn its keep. Pick your room type in the calculator above and it'll turn that into a straight steer instead of leaving you to weigh it up yourself.
Common questions
How much paint do I need per square metre?
One litre covers about 16 m² per coat on a normal wall, per Dulux's own coverage figures. A porous or previously unpainted surface will drink up more, so budget a bit extra for bare plaster.
Do I need two coats of paint?
Yes, for any real colour change. One coat is only enough for a touch-up in the exact same colour on a wall that's already that shade. Bare plaster, new drywall or a big jump in colour (dark over light, or the reverse) usually needs a third coat.
How much does paint cost per litre in Australia?
Roughly $7 to $10 a litre for a budget interior paint, and $19 to $27 a litre for a mainstream premium brand like Dulux Wash&Wear or Taubmans Endure, depending on can size, bigger cans work out cheaper per litre.
Does a tinted primer save money over just adding a third coat?
Not on Australian retail prices, no. A litre of primer/sealer/undercoat (Dulux 1Step Prep, Taubmans 3-in-1) runs $22–24, well above budget paint's $7–10/L, so primer plus two topcoats costs more in raw materials than three straight topcoats of the same paint. See our full breakdown for the worked numbers.
Sources
Electricity rates: AER Default Market Offer (NSW, SA, south-east QLD), Victorian Default Offer, and each remaining state's regulated tariff, current for 2026–27. Appliance figures: the energyrating.gov.au registration database (July 2026 snapshot). Methods and assumptions are described on each page.