Paint Calculator

Estimate how much paint you need for a room: wall area, coats, doors and windows deducted, with gallons and litres required.

Room length (ft)

Room width (ft)

Wall height (ft)

Number of coats

Doors

Windows

Include the ceiling

US gallons

1.91

Buy 2 × 1 gal

Litres

6.19

Buy 3 × 2.5 L

Paintable area

31.0 m²

333 ft² per coat

How this is calculated

Area = 2 × (length + width) × height − openings; Paint = area × coats ÷ coverage

Deductions assume a standard door of 1.9 m² (about 20 ft²) and a window of 1.4 m² (about 15 ft²). Coverage assumes 32.5 m² per US gallon (roughly 350 ft²) on a primed, smooth surface. Textured, porous or dark-to-light surfaces can cut coverage by 20–30%, so round up.

Cite this page

UnitConvertLab. (2026). Paint Calculator. UnitConvertLab. Retrieved from https://unitconvertlab.com/pt/tools/paint-calculator