How this calculator works
The formula: perimeter × wall height × floors = total wall area. Subtract doors (21 sq ft each) and windows (15 sq ft each), multiply by your coat count, divide by siding-specific coverage, round up.
Siding type matters a lot. Lap and fiber cement cover efficiently. Stucco and brick drink paint — that's why the calculator adjusts coverage per surface rather than using a single number.
How much paint does a house need?
| Home size & type | Siding paint (2 coats) | Trim (separate) |
|---|---|---|
| 1-story, 1,200 sq ft footprint | 8–10 gallons | 1–2 gallons |
| 1-story, 2,000 sq ft footprint | 12–15 gallons | 2–3 gallons |
| 2-story, 1,200 sq ft footprint | 14–18 gallons | 2–3 gallons |
| 2-story, 2,000 sq ft footprint | 18–22 gallons | 3–4 gallons |
| 2-story stucco, 2,000 sq ft | 24–30 gallons | 3–4 gallons |
Estimates assume average door/window counts and 9 ft ceilings.
How siding type changes coverage
- Lap siding / fiber cement: smoothest exterior surface. ~300 sq ft per gallon.
- Wood shake / board & batten / T1-11: textured. ~250 sq ft per gallon.
- Stucco: highly porous. ~200 sq ft per gallon.
- Brick / rough masonry: deepest texture. ~175 sq ft per gallon, sometimes less.
How weather affects exterior paint
Exterior paint is sensitive to conditions when applied. Read this before you buy:
- Temperature: most modern latex exteriors can be applied between 35°F and 90°F. Below that, the paint doesn't coalesce. Above, it dries too fast and leaves lap marks.
- Humidity: 40–70% is the sweet spot. Very high humidity slows drying; very low can cause flashing.
- Sun: don't paint in direct midday sun. Follow the shade around the house as the day goes on.
- Rain: no rain in the forecast for at least 24 hours after application. Modern paint cures faster than old oil-based, but wet paint still streaks.
Don't forget trim
Trim is painted separately in a different sheen (usually semi-gloss) and often a different color. Budget 1 gallon of trim paint per every 6–8 gallons of siding paint. For a standard 2-story home, that's 3 gallons of trim paint.
Doors count as trim, not siding, since they're typically painted in the trim color and sheen.
Common exterior painting mistakes
- Skipping prep. Exterior paint needs a clean, dry, sound surface. Pressure-wash and scrape loose paint before you ever open a can.
- Not spot-priming. Bare wood, patched spots, and chalking surfaces need primer even if the rest of the wall doesn't.
- Ignoring caulking. Re-caulk gaps around trim, windows, and doors before painting — it's part of the job, not optional.
- Buying too little. Exterior paint can vary between batches. Buy it all at once, or ask the store to "box" it (mix batches together).
FAQ
How much paint do I need for the outside of a house?
A typical 2,000 sq ft single-story home with lap siding needs 12–15 gallons for two coats plus 2–3 gallons for trim. A two-story of the same footprint needs 18–22 gallons for siding.
How much does exterior paint cover per gallon?
~250–300 sq ft on lap siding, 200–250 on stucco, 150–200 on rough brick. Textured surfaces soak up more paint.
Does the exterior need primer?
Prime bare wood, patched spots, weathered siding, and chalking or peeling areas. You don't need to prime a full wall of sound existing paint — spot-prime instead.
How many coats of exterior paint?
Two coats is standard. One is only acceptable when refreshing the exact same color with a premium self-priming paint over sound existing paint.