If you enter a perimeter, length and width are ignored.
These results show the net exterior wall area after subtracting openings and the estimated paint volumes including your coats and waste allowance. Values are rounded and intended as planning estimates.
Quick guide (with a simple example)
This calculator turns exterior wall sizes into paint volume by combining area, coverage per coat, and allowances.
- Net wall area = gross wall area − openings (doors, windows, and other exclusions).
- Topcoat (per coat) = net area ÷ coverage (ft²/gal).
- Total topcoat = per-coat × coats × absorption × (1 + waste%).
- Primer uses the same idea with primer coverage and primer coats.
Worked example (US units)
Suppose your net paintable area is 2,400 ft², topcoat coverage is 350 ft²/gal, topcoat coats = 2, waste = 10%, absorption = 1.00. Then topcoat ≈ (2,400 ÷ 350) × 2 × 1.10 ≈ 15.1 gallons. Use the built-in can planner to pick practical can sizes.
Common pitfalls
- Rough or porous exteriors (stucco, bare wood, new cement board) often need more paint than label coverage.
- Spraying, masking, and windy conditions typically increase waste compared with careful rolling.
- If you paint multiple colors or accent areas, estimate them separately.
How to use this exterior paint calculator effectively
Estimate exterior paint from the surface you can actually paint: gross wall area minus windows, doors, garage doors, and other openings. Then choose coats, coverage, waste, absorption, and primer so the result matches the product label and wall texture.
Choose the right input mode
- Building dimensions are fastest for a rectangular house or simple perimeter.
- Wall-by-wall entry is better when gables, additions, or different heights matter.
- Known area is useful when you already measured net wall area from plans or another estimator.
Coverage and waste assumptions
Label coverage assumes a smooth surface and ideal application. Rough stucco, bare wood, masonry, spraying, wind, and color changes can require a higher waste allowance or lower coverage. Primer should be estimated separately when the surface is new, patched, porous, or changing from dark to light.
See also
FAQ
How accurate are these exterior paint estimates?
Estimates use the wall area you enter, coverage presets, absorption multipliers, and your waste allowance. Real projects can vary with product formulation, spraying vs rolling, weather, and texture. Always size up if unsure and follow the product label.
What defaults are used for coverage and openings?
Defaults assume 400 ft²/gal for flat, 350 for eggshell/satin, 300 for semi-gloss, and 200 for primer with 10% waste. Door and window areas default to 21 and 12 ft² (1.8 m² and 1.2 m²). Override coverage or absorption if your paint line differs.
What should I measure first for exterior paint coverage?
Start with wall area, openings, coat count, coverage rate, and waste allowance. Keep surface type and product coverage assumptions visible before estimating cans.
Why can exterior paint coverage results differ from nearby tools?
Differences usually come from surface area, coverage rate, coat count, texture, and waste allowance. Match those assumptions before comparing this result with another CalcBE page, spreadsheet, or external tool.
How should I judge the reliability of the result?
Use the displayed result as reliable for the stated surface area, coverage rate, coat count, texture, and waste allowance. For official reporting, regulated work, or purchasing decisions, verify the inputs against the source document or provider rule you must follow.
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