Exterior Siding Paint Calculator
Siding area is the whole house wrapped once: the wall perimeter times the total wall height, minus the openings. Rough wood, stucco and brick cut coverage sharply — this plans painting the existing siding, never replacing it.
About 14 gallons for 2,358 sq ft of siding at 2 coats. Exterior siding area is wall perimeter × total wall height minus openings; stucco, rough wood and brick cut coverage sharply (toward 150–250 sq ft/gal) and often need a primer/sealer — this plans painting the existing siding, never replacing it.
Calculator inputs
Exterior siding is the same identity as an interior wall, scaled up to the whole house: perimeter × total wall height, minus doors and windows, × coats ÷ coverage. The wrinkle outdoors is coverage — lap and vinyl behave like smooth drywall, but stucco, rough-sawn wood and brick are porous and can cut a gallon’s reach nearly in half, often needing a primer/sealer coat as well.
This tool plans painting the siding you already have. It is not a siding-replacement or cladding estimator — that is a different trade. For the dollar side, carry the area into the exterior house painting cost tool.
Formula
gross siding = wall perimeter × total wall heightnet siding = gross siding − (doors × 21 + windows × 15)gallons = ceil( net siding × coats ÷ coverage per gallon )
Worked example
A two-story house, 140 ft perimeter, 18 ft total wall height, two doors and eight windows, two coats, 350 sq ft/gal:
- Gross = 140 × 18 = 2,520 sq ft.
- Openings = 2 doors (42) + 8 windows (120) = 162 sq ft; net = 2,520 − 162 = 2,358 sq ft.
- Gallons = ceil(2,358 × 2 ÷ 350) = ceil(13.47) = 14 gallons.
On stucco or rough wood, drop the coverage toward 200 sq ft/gal and add a primer/sealer coat — the gallon count climbs fast.
Wrap the house, mind the surface
Sizing an exterior, in order:
- Height is per story. Roughly 9–10 ft per floor to the eaves; do not forget gables and dormers — add each gable triangle (½ × base × height).
- Coverage is surface-driven. Smooth lap/vinyl 300–400; stucco, rough wood and brick 150–250 and thirstier on the first coat.
- Prime the bare and the porous. New wood, bare masonry and heavy repairs want a primer/sealer; size it with the primer calculator.
- Trim and soffits are extra. Fascia, soffit and window trim are a separate color/enamel — keep them off the siding count.
- Pre-1978 homes: scraping or sanding old exterior paint is EPA RRP territory — use a certified firm; this tool plans coverage, not lead-safe prep.
Reference table
| Paint × surface | Coverage (sq ft/gal, one coat) |
|---|---|
| Smooth / previously-painted drywall (latex) | 350–400 |
| New / primed drywall | 300–350 |
| Textured or porous interior wall | 250–300 |
| Smooth wood / trim (enamel) | 350–400 |
| Bare / rough wood | 200–300 |
| Exterior lap / vinyl siding (smooth) | 300–400 |
| Stucco / rough masonry | 150–250 |
| Brick (unpainted) | 100–200 |
| Concrete / block | 200–300 |
| Deck / fence (semi-transparent stain) | 200–300 |
| Primer (drywall / general) | 200–300 |
Labeled published planning snapshot — the can’s stated spread rate wins. Rough, porous or thirsty surfaces sit at the low end; a big color change or a light coat pushes you toward the high end. Full matrix: paint coverage by surface.
Frequently asked questions
How many gallons to paint a house exterior?
Depends on the wall area and the surface. A two-story house with ~2,358 sq ft of siding at two coats and 350 sq ft/gal needs about 14 gallons. Rough or porous siding at lower coverage needs noticeably more.
How do I measure exterior wall height?
Estimate about 9–10 ft per story from grade to the eaves, then add the gable triangles (½ × base × peak height) for the wall area under the roof peaks.
Does stucco or brick need more paint?
Yes — they are porous, so coverage drops to roughly 150–250 sq ft/gal and the first coat soaks in. Expect a masonry primer/sealer plus your finish coats. Set the coverage input to the low end.
Is this for replacing siding?
No. This plans painting the existing siding only. Replacing or installing siding, gutters or cladding is a separate trade and not covered here.