Exterior Paint Calculator
How much paint for the outside of the house?
How this is calculated
- Total wall area = 2 × (length + width) × wall height
- Deduct 20 sq ft per door, 15 sq ft per window
- Paintable area × coats ÷ coverage per gallon = exact gallons
- Buy amount rounds up to the next half gallon
Common questions
How much paint to paint my house exterior?
A 30 × 20 single-story (9 ft walls) has 900 sq ft of wall; after 2 doors and 8 windows that is 740 sq ft paintable. Two coats at 350 sq ft/gal = about 4.25 gallons — buy 4.5 to 5. Textured siding or a big color change pushes it to 6+.
Why does exterior paint cover less than interior?
Weathered siding drinks primer, textured surfaces (stucco, rough-sawn cedar, brick) have far more actual surface than their flat area, and exterior paints are formulated with more resin for UV and flex. Trust the can's exterior coverage number, not the interior 400.
How do I paint over brick?
Clean (TSP or pressure-wash, dry 24h+), prime with a masonry-conditioning primer, then 100% acrylic exterior paint at 200-250 sq ft/gal — brick will use nearly double the paint of smooth siding. Know that painted brick is a one-way door: stripping it later is a monumentally messy job.
What is the best time of year to paint outside?
The label rules: air and surface temps 50-90°F (some premium lines allow 35°F), no rain in the forecast for the coat's cure window (4-6h), low-ish humidity, and avoid direct blazing sun — it flash-dries before the paint levels. Early summer morning starts are the classic plan.
How often does exterior paint need redoing?
Wood siding: 4-7 years (stain less). Quality acrylic on fiber cement: 10-15. Aluminum/vinyl-safe coatings: 10+. Brick: 15-20. South and west faces weather 2-3× faster than shaded sides — when the chalky rub-off appears, repaint before the substrate underneath starts failing.