The Exterior Paint Calculator works out how many gallons of paint you need for the outside walls of a house. It calculates the paintable area from the house perimeter, wall height and gable ends, subtracts doors and windows, and uses a coverage rate for your surface type — smooth siding, rough wood, stucco, brick or split-face block.
Exterior Paint Calculator
Gallons of exterior paint for a house by surface type — smooth siding, rough wood, stucco, brick or block.
Rough and porous surfaces absorb more paint, so the same house can need very different amounts depending on its cladding. For a price estimate, see the Exterior House Painting Cost Calculator.
Formula
Area = P × H + gables × ½ × gable width × gable height − openings
Paint = area × coats ÷ surface coverage
Where P = house perimeter and H = wall height to the eaves.
Coverage by Surface (Calculator Defaults)
| Surface | Approx. ft² per gallon |
|---|---|
| Smooth siding | ≈ 350 |
| Wood shingles / rough-sawn | ≈ 300 |
| Brick | ≈ 250 |
| Stucco | ≈ 200 |
| Split-face block | ≈ 150 |
These are rough guides; your paint’s data sheet gives the figure for each surface.
How the Calculation Works
Step 1: Perimeter × wall height.
Step 2: Add gable triangles and subtract openings.
Step 3: Multiply by coats and divide by the coverage for your surface.
Example Calculation
Given: 160 ft perimeter, 18 ft walls, 2 gables 30 ft wide × 6 ft high, 250 ft² of openings, smooth siding, 2 coats
- Walls = 160 × 18 = 2,880 ft²
- Gables = 2 × ½ × 30 × 6 = 180 ft²
- Paintable = 2,880 + 180 − 250 = 2,810 ft²
- Paint = 2,810 × 2 ÷ 350 ≈ 16.06 gal → 17 gallons
The same house in stucco (≈200 ft²/gal) would need about 28.1 gallons.
Material Estimation Notes
- Trim, doors, shutters and soffits are often a different paint — calculate them separately.
- Primer on bare wood or repairs is extra.
- Five-gallon pails can be more economical for large jobs.
Frequently Asked Questions
How much paint do I need for the exterior of a house?
Paintable wall area × coats ÷ coverage for your surface.
How do I find the perimeter of my house?
Add the lengths of all outside walls.
Why does stucco need more paint?
Its rough, porous texture has more surface and absorbs more paint.
How many 5-gallon buckets do I need?
Gallons ÷ 5, rounded up.
Should I subtract windows?
Yes — enter their total area.