Paint Calculator
Interior rooms: walls, ceiling, doors and windows.
Exterior painting
How much paint does the outside of a house need?
Enter the house footprint and wall height and this exterior paint calculator returns the gallons for siding, stucco, brick or masonry — windows, doors and garage doors are deducted automatically. A typical 40 × 30 ft one-story house needs about 7 gallons of paint for two coats on siding, or closer to 11 gallons on porous stucco or brick.
A house exterior is painted wall by wall, not by the building's interior square footage. Add each wall as its own run with its own length and height — two-story walls, gables and mixed siding over brick are no problem — and the estimator applies siding, stucco or brick coverage rates, deducts windows and garage doors, and returns the gallons per coat for your whole house.
Frequently asked questions
How much exterior paint do I need for a 2,000 sq ft house?
For a typical one-story house with about 1,200–1,500 sq ft of paintable walls, buy 6–8 gallons of exterior paint for two coats on siding, or 9–12 gallons on stucco or brick. The footprint-size calculator above gives your exact figure.
Does exterior paint cover more or less than interior paint?
Exterior paint is formulated to resist weather and usually covers a similar 250–400 sq ft per gallon. On rough or porous siding it covers less, so always measure the wall area rather than guessing by house square footage.
Do I need primer before exterior paint?
Prime bare wood, new stucco, patched areas and chalky old paint. Primer seals the surface, evens out the "suck" and typically adds one extra coat-equivalent of material to your total.
Should the house be painted one or two coats?
Two finish coats are the professional standard, especially when the color changes or the old paint is faded. A same-color repaint on sound paint can occasionally get away with one coat — check a test patch in direct sun.
How do I measure my house exterior for a paint estimate?
Measure the length of every exterior wall and multiply it by that wall's height, then add the runs together and deduct large openings. For two-story walls or gables, enter each section as a separate wall run in this calculator and it totals them for you.
Why do stucco and brick need more paint than wood siding?
Masonry surfaces are porous and absorb far more paint than smooth siding — coverage drops from roughly 350–400 sq ft per gallon on siding to about 200–250 sq ft on stucco or brick. That is why the same house needs about 11 gallons there versus 7 on siding.
Exterior Paint Calculator
Imperial (ft / gal)
ft
ft
ft
Sq ft covered per gallon per coat on that surface.
× 12 sq ft
× 21 sq ft
× 120 sq ft
sq ft
Add gable triangles you measured separately.
Coats
Enter your house size to see the result.
–
gallons
Does not include trim, fascia or soffits — paint them with their own estimate.
How it works
How to use this exterior paint calculator
1Measure the walls
Multiply the footprint perimeter by the wall height. For a rectangular one-story house that means length and width plus eave height — exactly the fields above.
- Add gable triangles separately as their own square footage.
- For two-story houses, repeat for each level or measure total wall height.
- Don't paint underneath roof overhangs — that is soffit trim.
2Pick the surface
The substrate decides how far a gallon goes: smooth siding drinks the least, while stucco and old brick soak up paint like a sponge.
- Wood siding / cedar: ~350 sq ft per gallon per coat.
- Stucco and textured coatings: ~250 sq ft.
- Brick and masonry: ~200 sq ft — or use a specialized elastomeric coating.
3Deduct openings
Windows (≈12 sq ft each), entry doors (≈21 sq ft) and garage doors (≈120 sq ft for a two-car) come out of the paintable area. If your home has a door wall or sliding glass doors, add a few extra square feet of deductions per unit.
The math
Exterior paint quantity formula
Wall area = 2 × (length + width) × wall height − windows × 12 − doors × 21 − garage doors × 120 (+ any gable area you measured)
Gallons needed = (wall area × coats) ÷ coverage per gallon
Worked example — 40 × 30 ft home, 10 ft walls, siding (350 sq ft/gal), 6 windows, 2 doors, 1 garage door, two coats:
Walls: 140 × 10 = 1,400 − 72 − 42 − 120 = 1,166 sq ft; × 2 coats = 2,332 ÷ 350 = 6.7 gal → buy 7 gallons.
Walls: 140 × 10 = 1,400 − 72 − 42 − 120 = 1,166 sq ft; × 2 coats = 2,332 ÷ 350 = 6.7 gal → buy 7 gallons.
Coverage guide
Exterior paint coverage by surface
Typical square footage covered per gallon of exterior acrylic latex, one coat. Two coats are standard for color changes and bare wood.
| Surface | Sq ft / gallon | Notes |
|---|---|---|
| Smooth wood siding | 350–400 | Prime bare cedar first |
| T-111 / rough plywood | 250–300 | Seal the edges & seams |
| Stucco | 200–250 | Use textured-coating rated paint |
| Brick / block | 150–200 | Elastomeric for foundation walls |
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