Paint planning guide · Updated November 3, 2026
Estimate paint for walls from your measurements
Measure wall area, account for doors, windows and coats, then divide by the coverage stated for your chosen paint. Actual coverage varies by product and surface.
Quick answer: how much wall paint should I plan for?
Add the area of the walls you will paint, subtract openings you will leave unpainted, multiply by the planned number of coats, then divide by the coverage per gallon stated for your selected product. Round up to a practical package amount. This is a planning estimate; actual coverage varies with the product, surface texture and condition, application method and paint left on tools. Reviewed November 3, 2026.
How do I measure wall area?
Measure each wall's length and height in the same units. Multiply length by height for each wall, then add those areas. For a room with four rectangular walls, this is the sum of each wall's length × height; using room perimeter × wall height is equivalent when the walls share one height and the room is a simple rectangle. Measure sloped or irregular sections separately.
Should I subtract doors and windows?
For a closer wall-only estimate, measure the openings you will not paint, calculate each opening's area, and subtract their total from gross wall area. If you plan to paint the trim, frame or door, do not treat that part as unpainted wall; estimate those surfaces separately. Sherwin-Williams describes calculating the square footage to be coated before dividing by product coverage.
How do coats affect the estimate?
Multiply net paintable area by the number of coats planned before dividing by coverage. Follow the selected product's label and technical instructions for coat requirements, recoat times and preparation. A primer coat, if needed, is a separate material estimate.
What coverage value should I enter?
Use the coverage for the exact product and conditions you intend to use, taken from its current label or product data sheet. Do not assume a universal square-feet-per-gallon yield: manufacturer guidance says coverage is approximate and depends on factors such as substrate texture, surface condition and application. Keep your own coverage value in the calculator and change it only when your product information changes.
Try the paint calculator
Use the Paint link in the site navigation to open the calculator. Enter your measured paintable area, coat count and product-specific coverage assumption. The calculator keeps the values you enter in place after calculating; it does not substitute a default product yield.