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Paint Calculator (Wall & Ceiling)
Measure the room, deduct doors and windows, choose coats and coverage, and get the paint and primer you need with the best mix of can sizes.
How this is calculated
Paintable area = wall perimeter × height (+ ceiling if selected) − doors (about 21 sq ft each) − windows (about 15 sq ft each).
Paint = area × coats ÷ coverage per litre per coat. Primer uses one coat. Can sizes are picked to cover the litres with the least waste.
Frequently asked questions
How many square feet does one litre of paint cover?
Interior emulsions typically cover 90–140 sq ft per litre per coat on a smooth, primed wall. Check the product label and enter it in the calculator.
Do I need two coats?
Yes for almost all repaints and any colour change. Deep colours over light walls may need a third coat.
Estimates are for planning only. Prices vary by city, brand, design and site conditions — get itemised quotes before you commit.