Exterior Paint Calculator
Gallons of exterior paint for a house by size and coats.
Paint to buy
9 gal
Wall area
1,260 sq ft30×40 footprint, 9 ft walls (gross)
Paint (2 coats)
8.4 gallonsbuy 9 gal
Coverage
300 sq ft / gallonper coat, exterior surface
Paint cost (est.)
$405~$45/gal exterior
Doing this for work? Estimate the whole job in minutes.
JRIQ turns plans and site photos into full material + labor estimates with AI — built by the team behind these calculators.
Try it free →
A fresh coat of exterior paint is the highest-impact upgrade a house can get, and it protects the siding underneath. Like interior painting, it's 90% prep — wash, scrape, prime — and the right weather window.
DifficultyIntermediate
TimeSeveral weekends for a whole house including prep
SkillsComfortable on ladders and with prep work; the painting itself is easy
Tools you'll need
- Pressure washer
- Scrapers and a sander
- Brushes, rollers, or a paint sprayer
- Exterior primer and paintable caulk
- Drop cloths and an extension ladder
Step by step
- Wash the housePressure-wash off dirt, chalk, and mildew and let it dry fully — paint won't bond to a dirty or damp surface.
- Scrape and sandScrape loose and peeling paint, sand the edges smooth, and remove anything that isn't firmly stuck.
- Prime and caulkSpot-prime bare wood and stains, then caulk gaps around trim, windows, and joints to seal out water.
- Paint in the right weatherAim for mild, dry days (roughly 50–85°F, low humidity, out of direct hot sun). Work top to bottom and keep a wet edge.
- Two coatsApply two coats for durable, even coverage and color — one coat over old paint rarely lasts.
Common mistakes
Not washing first
Paint peels off dirt, chalk, and mildew. Pressure-wash and let it dry before anything else.
Painting over peeling paint
New paint is only as stuck as what's under it. Scrape and sand loose paint first.
Painting in bad weather
Too hot, cold, humid, or in direct sun and paint won't cure right. Pick a mild, dry window.
Skipping primer on bare wood
Bare and weathered wood needs primer to seal and bond, or the topcoat fails early.
Safety
- Set ladders on firm, level ground and never overreach.
- Homes built before 1978 may have lead paint — test and follow lead-safe practices before sanding.
Frequently asked questions
How much exterior paint do I need?
Enter your home's footprint, wall height, and coats above — the calculator returns gallons at ~300 sq ft per gallon.
What temperature is best for exterior paint?
Roughly 50–85°F with low humidity and out of direct hot sun; check the can for the product's range.
One coat or two?
Two coats for lasting protection and even color, especially over a color change or bare-wood repairs.
Next steps for this project
Sources & references
- EPA lead-safe (RRP) guidance for pre-1978 homes