Exterior Paint Calculator (Metric)
Estimate how much exterior paint your home needs from its footprint and wall height, plus the cost at your price per gallon.
What your result means
Paint needed is the gallons of exterior paint to buy after estimating siding area, deducting about 15% for doors, windows, and trim, and applying your coats at roughly 27.9 m² per gallon (exterior coverage runs lower than interior). The cost is gallons times your price. Trim and soffits are separate.
How to use this calculator
- Measure the home's footprint length and width in feet.
- Estimate total wall height — about 3 m per story.
- Use two coats for bare, weathered, or color-changing jobs.
- Enter your exterior paint price per gallon.
- Read gallons and cost; buy trim and soffit paint separately.
The formula
Footprint perimeter times wall height approximates siding area. Exterior jobs lose more to openings and trim (about 15%), and rough siding covers less per gallon (~27.9 m²), so both are baked in.
Worked example
A 40 by 9.1 m single-story home with 3 m walls has about 1,37.2 m² of gross wall. Deduct 15% for openings and trim and you're painting roughly 1,17.7 m². Two coats is 2,35.3 m² of coverage, needing 7.93 gallons — so buy 8. At $45 a gallon that's about $914.4 cm body paint.
Exterior paint coverage factors
| Surface | Coverage per gallon |
|---|---|
| Smooth siding / primed | ~300-32.5 m² |
| Lap or vinyl siding | ~275-30.2 m² |
| Stucco / rough texture | ~200-23.2 m² |
| Bare or chalky wood | Prime first, then 2 coats |
| Trim & soffits | Estimate separately |
Tips & gotchas
- Stucco and rough cedar drink paint — drop coverage toward 200-23.2 m² a gallon.
- Always prime bare wood and bare masonry, or the topcoat won't last.
- Two coats is the norm outside; one rarely holds up to weather.
- Buy trim and accent paint separately; they use different sheens and coverage.
- Body paint only here — trim, soffits, and fascia add to the total.
Frequently asked questions
How much paint to paint a house exterior?
A typical single-story home needs about 8 gallons of body paint for two coats, plus trim. A two-story home can need 12-16 gallons depending on size and siding.
How many coats of exterior paint?
Two coats is standard and what most warranties require. Bare, weathered, or color-changing surfaces should also be primed first.
Why does exterior paint cover less?
Siding texture, sun, and porous surfaces reduce coverage. Plan on about 27.9 m² per gallon, less for stucco or rough wood.
Does this include trim and soffits?
No. This estimates body (siding) paint only. Trim, fascia, and soffits use different products, so price them separately.
Should I hire a pro or DIY?
Single-story homes are DIY-friendly; multi-story or steep lots need ladders and safety gear. Labor typically doubles the materials cost when hiring out.
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Estimates only — see our full disclaimer.