Paint Coverage Calculator
Calculate the exact number of litres of paint required for any room or surface. Accounts for the number of coats and the spread rate of your chosen paint product.
About this calculator
Paint quantity is calculated by multiplying the total surface area by the number of coats applied, then dividing by the coverage rate of the paint. The formula is: Paint (litres) = (totalArea × coats) / coverage, where coverage is measured in m² per litre. Typical interior emulsion covers 10–12 m²/L, while masonry or exterior paint may only cover 5–8 m²/L. The coverage rate is always stated on the paint tin. Applying two coats is standard practice for most interior repaints; three coats are needed when making a dramatic colour change or painting bare plaster. Summing up all surfaces — walls, ceilings, and trim — before entering the total area gives the most accurate result.
How to use
You are painting a bedroom with a total wall and ceiling area of 45 m², applying 2 coats of emulsion rated at 11 m²/L. Step 1 — Enter Total Surface Area = 45 m². Step 2 — Enter Number of Coats = 2. Step 3 — Enter Paint Coverage = 11 m²/L. Step 4 — Paint = (45 × 2) / 11 = 90 / 11 ≈ 8.18 litres. You would purchase two 5-litre tins (10 litres total) to have a small buffer for touch-ups. Subtract door and window areas from the total before entering if you want a tighter estimate.
Frequently asked questions
How do I measure total surface area for a room with multiple walls and a ceiling?
Measure the length and height of each wall individually and multiply to get each wall's area, then sum all four walls. Add the ceiling area (room length × room width). Subtract the area of each door (typically 1.8 m²) and each window (typically 1.2 m²) if you want a precise figure. Using a laser distance measurer makes this faster and more accurate than a tape measure for larger rooms.
What paint coverage rate should I use for different types of surfaces and paint?
Coverage varies significantly by paint type and surface porosity. Interior matt or silk emulsion typically covers 10–12 m²/L on previously painted walls. Bare plaster absorbs more paint and may only yield 6–8 m²/L on the first coat. Exterior masonry paint covers 5–8 m²/L, while gloss or satin trim paint covers around 14–16 m²/L. Always use the figure printed on the specific tin you are buying for the most accurate result.
How many coats of paint do I need when changing wall colour significantly?
When painting over a dark colour with a lighter one, or vice versa, two coats are rarely sufficient — three or even four coats may be needed for full opacity. Using a tinted primer that closely matches your new colour reduces the number of topcoats required and saves money overall. When repainting a similar colour on well-prepared walls, a single coat of quality paint can sometimes suffice, though two coats always produce a more durable and even finish.