How to use this calculator
- Measure the house perimeter. Walk around the house and add up the wall lengths. Two-story homes — measure first story + second story separately.
- Multiply by wall height. Single story = perimeter × 9 ft (typical). Two stories = perimeter × 18 ft. Subtract gable triangles or measure them separately.
- Subtract openings. A typical window is 15 ft²; a door is 21 ft². Subtract these from the wall area.
- Pick coats. Two coats over existing paint is standard. New, primed siding may need three.
Formula
Gallons = (Wall ft² ÷ 250) × number of coats
Worked example
A 1,800 ft² two-story house has roughly 2,000 ft² of siding. Two coats = 4,000 ft² ÷ 250 = 16 gallons of exterior paint. Add 2 gallons for trim and 2 gallons of primer if any siding is bare or weathered → ~20 gallons total.
Common project sizes
Quick reference for the most common exterior paint calculator use cases. Use these as a sanity check on your calculator inputs.
| Project | Dimensions | Result |
|---|---|---|
| 1,000 ft² single-story (cottage/cabin) | ~1,100 ft² siding | 9 gal body · 2 gal trim · 2 gal primer |
| 1,500 ft² ranch | ~1,650 ft² siding | 14 gal body · 2 gal trim · 2 gal primer |
| 2,000 ft² 2-story | ~2,200 ft² siding | 18 gal body · 3 gal trim · 3 gal primer |
| 2,500 ft² 2-story | ~2,750 ft² siding | 22 gal body · 3 gal trim · 3 gal primer |
| Stucco home (1,800 ft², 1-story) | ~2,000 ft² siding | 27 gal body · 3 gal trim (texture +35%) |
2026 cost reference
Typical retail price range in the United States for exterior paint. Local pricing varies by region, supplier, and grade — confirm with two or three quotes before ordering.
Per gallon (exterior premium)
$30 – $80
Builder-grade exterior is $30–$45/gal (Behr, Valspar). Mid-tier 100% acrylic is $45–$60/gal (Sherwin-Williams Duration, Benjamin Moore Aura Exterior). Specialty / lifetime-warranty paints are $60–$80/gal. For a 2,000 ft² home, materials run $500–$1,200; full-house exterior repaint hired out is $3,000–$8,000 depending on condition and prep work.
How we calculate this
Assumptions baked in
Same paintable-area formula as the interior calculator, but exterior coverage drops to 300 ft²/gal on smooth siding and 200 ft²/gal on rough cedar, stucco, or masonry. Two coats are required for any color change; one coat is acceptable only for refresh on identical-color surfaces. Trim paint is calculated separately — typical 1,500 ft² home needs 1–2 gallons of trim paint vs. 12–14 gallons of body paint.
Accuracy and margin of error
±15% on smooth vinyl or fiber-cement siding. Variance on cedar shake (highly absorbent first coat), stucco (rough texture eats paint), and masonry (porous, needs masonry sealer first) is larger — add 25% to the gallons for any of those surfaces. Two-color schemes (body + trim) often require a third color for shutters/doors; budget 1 quart for accents.
Edge cases this calculator does not handle
Power washing before painting is non-optional — paint applied over chalking, mildew, or surfacing dirt fails within 2 years. Use an acrylic latex over alkyd primer combination for raw or weathered wood; oil-based primers grip better but yellow under light. Spray + back-roll on rough surfaces gives better adhesion than pure rolling.
Cited sources for this page
The figures and rules above are anchored to the following normative references. We link the underlying claim to its standard — not as generic SEO trust signals, but so you can audit any number on this page against a primary source.
Exterior coverage drops to 250–300 ft²/gal on smooth siding and 150–200 ft²/gal on rough textures (cedar, stucco, masonry) per major manufacturer spec sheets.
Power-washing wood and siding to remove chalking and biological growth before repainting is required for warranty validity by Sherwin-Williams, Benjamin Moore, and Behr.
Tips for accurate results
- Buy 5-gallon buckets — exterior paint is significantly cheaper per gallon at that size.
- Always paint the soffits and fascia in the same color as the trim to keep the eye flowing up.
- Cool, overcast days are best for exterior painting — direct sun causes lap marks.
- Spray-and-back-roll on textured surfaces (stucco, rough cedar) for the best coverage.
Common mistakes to avoid
- Painting in direct sun — hot siding causes blistering and lap marks. Follow the shade around the house.
- Forgetting to caulk gaps before paint — paint cracks at every gap within a season. Caulk all trim joints, around windows and doors, with paintable acrylic-latex caulk first.
- Using interior paint outside to save money — interior paint has no UV stabilizers and chalks within 6 months.
- Skipping the second coat on the south- and west-facing walls — those get the most sun and need the full mil thickness for the warranty to apply.
When to consult a pro
A single-story home in good repair is achievable DIY over 2–3 weekends with a 4-ft ladder, a roller, and a 4" brush. Hire a professional painter for any 2-story home (extension-ladder work above 16 ft is the leading cause of homeowner injuries), heavily peeled siding (lead-paint-era homes especially — pre-1978 houses require RRP-certified painters), or stucco/textured surfaces that need spray-and-back-roll application. The labor savings on a full-house repaint are real but the prep work eats most of them.