Material calculator
Exterior paint calculator — gallons
Estimate exterior body paint from wall area, openings, coats, and surface coverage. Rough siding and stucco cover far less per gallon than smooth primed surfaces.
You'll need
8.5 gallons
Exterior paint
- Buy (whole gallons)
- 9 gallons
What this assumes
- 1800 ft² minus 2 doors at 21 ft² and 10 windows at 15 ft².
- 1608 ft² × 2 coats ÷ 380 ft²/gal.
Coverage rates & sources
Every number this calculator uses is a published engineering constant — not an estimate we made up. Here is exactly what it assumes and where each value comes from.
- Smooth/primed coverage: ~380 ft²/gal (350–400)Source: SW/Behr spec (smooth, primed)
- Textured-siding coverage: ~320 ft²/galSource: Manufacturer note: texture cuts coverage 15–35% (use mid)
- Rough/stucco/masonry coverage: ~250 ft²/galSource: Behr real-world rough-surface coverage (~250 ft²/gal)
- Default coats: 2 coatsSource: Manufacturer hide guarantee
- Door/window deductions: 21 / 15 ft²Source: Standard door/window planning areas (shared with paint calc)
Before you buy
- Exterior coverage drops a lot on rough surfaces; stucco, rough cedar, and split-face block can fall to about 250 ft²/gal or less.
- Trim and contrasting body colors are separate products.
- Bare, chalky, or previously unpainted siding usually needs primer; measure gross wall area and deduct only large openings.
This is a planning estimate, not a substitute for a pro's on-site measurement. For load-bearing, structural, or code-regulated work, confirm quantities with a licensed contractor.
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