Paint Coverage Calculator: Estimate Gallons or Liters for a Room
Learn how to estimate paint from wall area, ceiling area, number of coats, and product coverage without overbuying.
Measure the surfaces you will actually coat
For a simple room, estimate wall area by adding the wall lengths and multiplying by ceiling height. Add the ceiling separately when it will be painted. Doors, windows, built-ins, and large openings can be subtracted when their area is material to the estimate.
Use square feet for most US and Canadian supplier discussions, or square meters for metric projects. Do not mix the area unit with a coverage rate expressed in a different system.
Apply coats and product coverage
Required paint volume depends on total surface area × number of coats ÷ product coverage. Coverage on the can is a starting point, not a guarantee. Porous drywall, textured masonry, dark-to-light color changes, and application method can increase consumption.
Primer should be considered separately when the surface is new, patched, stained, chalky, or undergoing a major color change. The calculator is most useful when the coverage input reflects the product and surface you are actually using.
Plan the purchase in the supplier’s package size
The result may be displayed in liters or US gallons. Round up to practical container sizes and consider keeping a small amount of the final color for future touch-ups. Paint batches can vary, so buying all of the finish coat at once is often preferable for visible spaces.