Free Online Calculators
Wall paint in litres: room size, windows, doors & coats
Whether you're refreshing a single bedroom or renovating an entire house, knowing exactly how much paint to buy is one of the most important steps in any painting project. Buy too little and you risk running out mid-wall or facing colour mismatches between batches. Buy too much and you're wasting money on product you'll struggle to dispose of. Our free paint calculator takes the guesswork out of the equation entirely.
Our tool is designed to give you a precise estimate of the litres of paint needed for any room. It accounts for all the key variables that affect real-world paint consumption, delivering a reliable result in just a few seconds.
Once you enter these values, the calculator instantly displays the total litres of paint required, so you can walk into the hardware store knowing exactly what to buy.
Many homeowners underestimate the impact of small calculation errors. Consider a room that is 5 m × 4 m with a 2.5 m ceiling. The total wall area is 45 m². Subtract two standard windows (each 1.2 m²) and one door (1.8 m²) and you have roughly 40.6 m² to cover. With two coats at 10 m²/l coverage, you need approximately 8.1 litres. Rounding up to the nearest available tin size (for example, two 5-litre tins) ensures you have enough without massive overspend.
Leftover paint is classified as hazardous waste in many countries and cannot simply be thrown in the bin. Proper disposal often costs money. By calculating your needs accurately, you minimise waste and contribute to a more sustainable approach to home improvement. Our free paint calculator is your first step toward a smarter, greener renovation.
A child's room measuring 3.5 m × 3 m with a 2.4 m ceiling has roughly 31.2 m² of wall area. With one window and one door removed, the net area drops to about 27 m². Two coats at 10 m²/l means you need 5.4 litres — one standard 5-litre tin and a small top-up tin should cover it perfectly.
Larger open-plan spaces can feel daunting to estimate. A room that is 8 m × 5 m with a 2.7 m ceiling has a wall area of around 70.2 m². Even with several large windows and doors subtracted, you're likely looking at 55–60 m² of paintable surface — requiring 11–12 litres for two coats at standard coverage.
Older homes often feature ceiling heights of 3 m or more. This dramatically increases wall surface area compared to modern properties. A room that appears modest in floor area can require significantly more paint than expected. The calculator handles non-standard ceiling heights effortlessly.
Add up the perimeter of the room (all four wall lengths combined) and multiply by the ceiling height. Then subtract the areas of windows and doors. Our paint calculator does all of this automatically when you enter your room dimensions.
At a standard coverage of 10 m²/l, you'd need 3 litres for one coat or 6 litres for two coats. Always check the specific coverage rate printed on your chosen paint tin, as this can vary between products.
Our calculator focuses on wall surfaces. To calculate ceiling paint separately, enter the room's floor area (length × width) as an additional surface, or use the calculator a second time with those dimensions.
Coverage rate (or spreading rate) tells you how many square metres one litre of paint will cover on a smooth, prepared surface. It is always printed on the tin. Higher-quality paints often have better coverage, meaning you use less product overall.
Yes — if you're applying a light colour over a similar existing shade on a well-prepared surface, one coat is often sufficient. However, for colour changes, especially from dark to light, or for bright feature wall colours, two coats are almost always needed for a consistent, professional result.