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Free Paint Calculator —
Know How Many Tins to Buy
Work out how much paint to buy — not just litres, but the actual combination of Australian tin sizes to put in your trolley. Enter your wall area or dimensions, deduct doors and windows, set your number of coats, and the calculator does the rest.
How to use this calculator
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Enter your wall area directly, or enter total wall length and wall height.
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Deduct doors and windows — enter how many of each, and adjust the average window size if yours differ.
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Set the number of coats (two is standard for colour changes) and the coverage rate from your paint tin.
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Read off the litres needed with waste included, and the recommended tins to buy.
What this calculator assumes
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Coverage defaults to a typical acrylic rate of around 14–16 m² per litre per coat — check your specific product, as coverage varies between paints and surfaces.
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Standard door and average window sizes are deducted from the wall area; you can adjust the window size.
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Litres are converted to a practical combination of Australian retail tin sizes, so you're not buying 10 L when 6 L will do.
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New or porous surfaces (fresh plasterboard, bare render, timber) drink more paint on the first coat and usually need a sealer or primer first — that's calculated separately.
Frequently Asked Questions (F&Q)
FAQ 1
Question: How much paint do I need per square metre?
Answer: Most quality acrylic paints cover 14–16 m² per litre per coat on a sealed, smooth surface. So a 4 m × 3 m wall (12 m²) needs a bit under a litre per coat. Rough, porous or dark surfaces reduce coverage.
FAQ 2
Question: How many coats of paint do I need?
Answer: Two coats is standard for a colour change or new work. One coat can be enough when repainting in the same or a very similar colour. Going from dark to light often needs a tinted undercoat plus two topcoats.
FAQ 3
Question: Do I subtract windows and doors when calculating paint?
Answer: Yes — they can be a significant share of a wall. This calculator deducts them for you: just enter the number of doors and windows.
FAQ 4
Question: Does ceiling paint work the same way?
Answer: The maths is the same — area × coats ÷ coverage rate. Enter your ceiling area as the "wall area" and use your ceiling paint's coverage rate. Ceiling paints are usually flat acrylics with similar coverage.
FAQ 5
Question: Should I buy one big tin or several small ones?
Answer: Larger tins are cheaper per litre, but leftover paint is money on a shelf. The calculator suggests a tin combination that covers your job with minimal excess — and keeping a small amount of leftover for touch-ups is smart.