Calculate how many liters of paint you need for a wall or room based on area, number of coats, and coverage rate.
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This calculator estimates how much paint you need by multiplying the surface area by the number of coats you plan to apply, then dividing by the paint's coverage rate (how many square meters one liter can cover). Coverage rate varies meaningfully by paint type, surface texture, and application method, so the default of 10 m² per liter is a reasonable average starting point, but checking the specific figure printed on your chosen paint can will always give a more accurate result. The calculator automatically adds a 10% allowance on top of the base calculation to account for touch-ups, minor spills, and the natural unevenness of real-world application, which is a standard practice recommended by most paint manufacturers and professional painters. For the most accurate estimate, measure your wall area after subtracting doors, windows, and other openings, since paint is never actually applied to those surfaces. Buying slightly more than the exact calculated amount is generally wise, since matching a specific paint batch later for touch-ups can be difficult if colors vary slightly between production runs.
Buying paint feels like it should be a simple multiplication problem, and mathematically it is — but the number that trips people up most often isn't the area or the can size, it's the coverage rate, and specifically the habit of forgetting that a single coat almost never gives the finish most people actually want.
A single coat of paint, especially over a different existing color or bare drywall, typically shows faint variations in opacity: patches where the underlying surface still shows through slightly, or a visible difference in sheen between areas that received slightly more or less paint during application. Two coats is the standard recommendation from most paint manufacturers specifically because the second coat fills in those gaps left by the first, producing the uniform, opaque finish that photographs and looks even in person under different lighting.
Coverage rate itself is not a fixed law of physics — it depends heavily on the paint's specific formulation, the texture and porosity of the surface being painted, and even the application method (a sprayer, roller, and brush all lay down paint at meaningfully different rates). Manufacturers test and publish a coverage figure for their specific product, usually stated as an area per unit volume, and that printed number will always be more accurate for your specific paint than any generic default.
The 10% waste allowance added on top of the base calculation reflects a handful of real, unavoidable factors: a small amount of paint inevitably remains in the tray or roller at the end of a job, drips and minor spills happen even to careful painters, and touch-ups after the main job is done (fixing a missed spot, covering a scuff) draw from the same supply. Buying exactly the calculated minimum, with zero buffer, risks an inconvenient mid-project trip back to the store — often for a can from a slightly different batch that may not match perfectly in color.
Rough surfaces like textured walls, stucco, or unfinished wood absorb significantly more paint than a smooth, previously painted wall, sometimes requiring 20-30% more paint than the smooth-surface coverage rate would suggest — another reason the printed coverage figure, tested on the manufacturer's reference surface, is a starting estimate rather than a guarantee for every wall type.
The 10% allowance covers touch-ups, minor spills, and slightly uneven application, which is a standard buffer recommended by most paint manufacturers to avoid running short mid-job.
Yes, for a more accurate estimate, measure and subtract the area of doors, windows, and other openings from your total wall area before entering it here.
Most walls need two coats for even, opaque coverage, though a single coat may suffice for a touch-up in a similar existing color, and three coats are sometimes needed for very light colors over a dark existing wall.