Paint Estimate by Wall Area and Coats

Wall area starts with two lengths, two widths, and height.

For a rectangular room, wall area is 2 × (length + width) × height. Measure unusual walls separately. Subtract large doors and windows when accuracy matters; small openings can serve as a contingency.

Two coats double the coated area.

Primer and finish paint are separate products with separate coverage. Texture, porosity, color change, application method, and product data can reduce real coverage, so use the label for the selected product.

A fractional gallon is not always a purchasable unit.

Calculate each product separately and round up to available container sizes. Keep touch-up and batch consistency in mind, but do not inflate every input with overlapping waste factors.

Sanding and cutting can create hazardous lead dust.

EPA recommends determining whether lead-based paint may be present and using lead-safe practices; hiring a lead-safe certified contractor is the safer path for many projects. Estimating paint is not a clearance to disturb suspect coatings.