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QuantoObra

Exterior Paint Calculator

Estimate exterior paint for a house, garage or shed. Enter the footprint, wall height and gable ends — we'll deduct doors and windows and tell you how many buckets to buy.

Interior wallsWalls & ceilingExterior

Results update as you type.

Building

Measure by
ft
ft
ft

Triangles above the walls on the width sides.

ft

Eave to ridge.

Doors
ft
ft
Windows
ft
ft
Add another section Pro

Paint

ft²/gal

Per coat. See the can.

%
$/gal

Price of a 1-gallon can. 5-gallon buckets are priced ~12% cheaper per gallon.

Advanced

Pro

Upgrade to Pro for multi-room projects, primer, separate ceiling paint, saved projects and branded PDF quotes.

Paint needed

9.82gallons

Paintable area
1,339 ft²
161 ft² openings deducted
Walls / ceiling
1,339 / 0
ft²
Recommended cans
2× 5-gal
Estimated cost
—
Add a price

Shopping list

  • 25-gallon bucket — exterior paint

  • 1Exterior caulk, scraper & masking supplies

    Recommended

Add prices below to see a cost estimate.

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How we calculate

walls = 2 × (length + width) × wall height
gables = number of gables × ½ × width × gable height
paintable = walls + gables − doors − windows
paint = paintable × coats ÷ coverage × (1 + waste %)

Gables are assumed to sit on the width sides of the building (the usual layout for a simple gable roof). For complex houses, measure each face and use "Total wall area" mode — or, with Pro, add each section separately.

Estimating exterior paint like a pro

Professional painters measure the perimeter × height of each storey, add gables and dormers, then deduct only large openings like garage doors. Small windows are often not deducted on exteriors because the trim around them uses paint too.

  • Wood siding: 250–300 ft²/gal (two coats on weathered wood).
  • Vinyl or fibre-cement: 300–350 ft²/gal.
  • Stucco or brick: 150–250 ft²/gal — very porous, consider a masonry primer.

Buy exterior paint in 5-gallon buckets and "box" (mix) multiple buckets together to guarantee a consistent colour across the whole house.

Frequently asked questions

How much paint do I need for the outside of a house?

Measure the perimeter and wall height, add gable triangles, and subtract doors and windows. A 40 × 30 ft single-storey house with 9 ft walls and two gables has about 1,400 ft² net; two coats at 300 ft²/gal with 10% waste needs about 10 gallons.

How do I calculate gable area?

A gable is a triangle: ½ × base × height. For a 30 ft wide house with a ridge 8 ft above the eaves, each gable is ½ × 30 × 8 = 120 ft².

Why does exterior paint cover less?

Siding, stucco, brick and weathered wood are textured and porous, so they absorb more paint. Plan on 250–350 ft² per gallon (6–8 m²/L) and less for rough stucco or bare wood.

Do I need primer for exterior painting?

Prime bare wood, repairs, chalky surfaces and when switching from oil to latex. Pro users can add primer with its own coverage and price.

How many coats of exterior paint?

Two coats is standard for durability, especially on south and west faces. A single coat of a premium paint can work for a same-colour refresh in good condition.

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