Home & Garden · Maintenance planning
How to estimate paint for a room
Measure the walls, subtract doors and windows, multiply by coats, and divide by the coverage on the can. The calculator uses 350 square feet only as a stand-in.
Area, then the label
Wall area is the perimeter times the height, minus openings. Two coats are common. Divide by the square feet per gallon printed on the can you will buy. Until you have that can, the paint estimator uses 350 square feet per gallon so you can see the math.
Who this is for
A single rectangular room. Vaulted ceilings, stairs, and brick need a different measure.
Before you buy
- Measure length, width, and height in feet.
- Count doors and average windows. The tool subtracts 20 and 15 square feet as placeholders. Measure odd openings yourself.
- Decide if the ceiling is in the same color.
- Buy a little extra for touch-ups from the same batch when you can. Batches can differ.
Darker paint changes how bulb lumens look. Plan both together.
Limits
Lead paint in older homes is a health issue. If the building was built before 1978 in the United States, read EPA guidance on renovation before you sand. This page does not tell you how to disturb painted surfaces safely.
Questions readers ask
Why did I need more paint than the estimate?
New drywall, textured walls, and a color change from dark to light drink extra paint. The can’s coverage is for a typical smooth, primed surface.
Sources and methodology
Claims that depend on an outside authority are tied to the references below. Product details change. Confirm the current specification sheet before you buy or install anything.
- Paint quantity estimator — Tech Home Tips (original method), accessed September 20, 2026. States the 350 square foot assumption and the opening sizes used in the tool.
Parent topic: Home & Garden · Related tool: Room paint quantity estimator