Enter your room dimensions to calculate exactly how many litres of paint you need. Supports walls, ceiling and trim, multiple coats, and automatic deductions for doors and windows.
Choose how you'd like to enter measurements
Length and width of the floor, plus the wall height
Select which surfaces you're painting
Deducted from wall area
Deducted from wall area
Two is standard
Check the tin; 11 is typical
Size you plan to buy
Optional, for cost estimate
Tap to load common room sizes
Total Paint Required
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📐 Total Paintable Area--
🖌️ Coats Applied--
🪣 Tins to Buy--
💧 Litres Left Over--
💷 Estimated Cost--
Breakdown by surface
Estimates round up to whole tins so you have enough for touch-ups.Coverage varies by surface and paint type.
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How to Use the Paint Calculator
Estimating paint is simple with our free calculator. Choose metric or imperial units, enter the length, width and height of your room, then tick which surfaces you're painting — walls, ceiling, trim or any combination. Add the number of doors and windows so they can be deducted from the wall area, pick how many coats you plan to apply, and click "Calculate Paint Needed". You'll instantly see the total litres required, how many tins to buy, and an optional cost estimate.
How the Paint Estimate Is Calculated
Wall area is the room perimeter (2 × length + 2 × width) multiplied by the wall height. We then subtract roughly 1.8 m² for each door and 1.5 m² for each window. Ceiling area is length × width, and trim is estimated from the perimeter. The total surface area is multiplied by the number of coats and divided by your paint's coverage (spread rate) in square metres per litre. Finally, we round up to whole tins of your chosen size.
Choosing the Right Coverage
Coverage depends heavily on the surface and the paint. Smooth, previously painted plaster can reach 12-14 m² per litre, while bare plaster, masonry, textured walls and bold colour changes can drop to 6-8 m² per litre. Primers and undercoats also have their own spread rates. Always check the figure printed on the tin and enter it in the coverage field for the most accurate estimate.
Painting Tips to Save Paint
Prime bare or patchy walls first so your topcoat goes further. Use a quality roller with the correct nap for your surface, work in manageable sections, and keep a wet edge to avoid lap marks. Buying all your tins from the same batch keeps the colour consistent, and keeping a little left over makes future touch-ups effortless. For dark-to-light changes, budget for an extra coat rather than overloading each one.
Frequently Asked Questions
As a rule of thumb, one litre of emulsion covers roughly 10-12 square metres per coat on a smooth, primed wall. Rough, textured or unpainted surfaces absorb more, dropping coverage to around 6-8 m² per litre. Set your own spread rate in the coverage field to match the product on the tin.
Most jobs need two coats for an even, durable finish. A single coat may be enough when repainting a similar colour, while three coats are common when covering dark colours with a light one, or painting bare plaster after a mist coat.
Yes. Doors and windows aren't painted with wall paint, so subtracting them is more accurate. This calculator uses about 1.8 m² per door and 1.5 m² per window and removes them from the wall area automatically.
Ceiling area equals room length × width. The calculator includes the ceiling automatically when you tick the ceiling option, using the same spread rate and number of coats unless you change them.
It's wise to add 5-10% extra for touch-ups, spillage and future repairs, and to keep colours consistent by buying the same batch. This calculator rounds up to whole tins, which naturally builds in a small buffer.