Measure each exterior surface separately
This tool uses a rectangular wall run. For a house with several elevations, calculate each wall separately and combine quantities only when the same paint, color and finish will be used. Gables, trim, doors and railings need their own measurements.
A 40-foot wall with two windows
A 40 × 8-foot wall has 320 square feet of gross area. With the tool's assumed 20-square-foot door and two 15-square-foot windows, paintable area is 270 square feet. Two coats create 540 square feet of coverage demand. Adding 10% gives 594; at 250 square feet per gallon, that is 2.376 gallons, rounded up to three.
Coverage can change the purchase
| Coverage entered | Gallons including 10% | Whole gallons |
|---|---|---|
| 250 sq ft/gal | 2.376 | 3 |
| 350 sq ft/gal | 1.697 | 2 |
| 400 sq ft/gal | 1.485 | 2 |
This comparison illustrates sensitivity; it is not permission to choose a higher coverage to reduce the order. Use your product's coverage and preparation instructions for the actual surface. Roughness, porosity and application method affect consumption.
Price the preparation as well as the finish
Keep washing, scraping, patching, caulk, primer, masking, access equipment and disposal on separate lines. Record the number of coats and the areas excluded when comparing a contractor's quote with your materials budget.
For older painted surfaces, check EPA lead-safe renovation guidance before disturbing paint. This quantity calculator cannot assess lead hazards or prescribe a safe work method.