Building and decorating
Paint Calculator
Turn room measurements into litres and whole tins, using the coverage printed on your chosen paint.
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How to use this tool
1. Enter your own figures below, or choose Load example to try the worked example. Check the units beside each field.
2. Select Calculate to see the result and its breakdown. If you change an input, calculate again before copying or printing.
3. Use Copy summary or Print / save PDF to keep your assumptions and results together. Reset clears the form.
How the calculation works
Wall area is 2 × (length + width) × height, minus your total opening area. Optional ceiling area is length × width. Multiply the total surface area by coats, divide by coverage per litre, then add your allowance. Divide the unrounded litres by tin size and round up to whole tins.
Worked example
A 5 m × 4 m room at 2.4 m high has 43.2 m² of walls. Excluding 4 m² of openings and adding a 20 m² ceiling gives 59.2 m². Two coats at 16 m²/litre with 10% extra need 8.14 litres: three 4-litre tins, leaving 3.86 litres beyond that estimate.
Questions and assumptions
What this estimate includes
The 16 m²/litre default is a starting example consistent with Dulux topcoat estimates; your product label and substrate take precedence. The tool assumes flat rectangular surfaces and the same coverage for every coat. It does not optimise a combination of different tin sizes or determine preparation requirements.
Can I save or share my result?
Copy summary includes the current inputs and results. Print / save PDF creates a local report with the calculation scope and source links. Your figures are not added to the page URL or stored by this tool. Refreshing clears the form.
Sources and further reading
Built and maintained by Custom Logic. Page updated .