Exterior Paint Calculator
Calculate how many gallons of exterior paint you need for your house siding, plus primer and trim paint, with instant cost estimates.
How to Calculate Exterior Paint
Estimating exterior paint starts with the paintable surface area of your walls. Measure the perimeter of your house — the total distance around the outside — and multiply it by the wall height from foundation to eaves. A single-story house with a 140-foot perimeter and 9-foot walls has 1,260 square feet of wall area. For a two-story house, use the full height to the second-story eaves, typically 18 to 19 feet.
Next, add the gable ends. A gable is the triangular section of wall under a pitched roof, and each one adds roughly half of the gable width times the gable height in area. For a typical house that works out to about 75 square feet per gable, which is the flat figure this calculator uses. Then subtract the areas you will not paint: doors and garage doors at about 21 square feet each, and windows at about 15 square feet each.
Finally, divide the paintable area by your paint's coverage rate and multiply by the number of coats. Coverage depends heavily on surface texture — smooth siding covers around 350 square feet per gallon, while rough stucco or brick can drink up a gallon in just 225 square feet. Round up to whole gallons, since paint is sold by the gallon and you want the same batch number for color consistency. The calculator also estimates primer at roughly 300 square feet per gallon and trim paint at about one gallon per 150 linear feet of trim.
Exterior Paint Coverage by Surface
Surface texture is the single biggest variable in exterior paint coverage. Porous, rough surfaces hold more paint in their texture and absorb more into the substrate, which lowers the effective coverage per gallon.
| Surface Type | Coverage per Gallon | Notes |
|---|---|---|
| Smooth (vinyl siding, Hardie panel, smooth wood) | ~350 sq ft | Best coverage; paint sits on the surface |
| Lightly textured (rough-sawn wood, fiber cement lap) | ~300 sq ft | Grain and lap lines absorb extra paint |
| Rough (stucco, brick, masonry, split-face block) | ~225 sq ft | Deep texture can cut coverage by a third or more |
These figures assume paint applied at the manufacturer's recommended spread rate with a roller or sprayer plus back-rolling. Spraying without back-rolling can use 10 to 20 percent more paint due to overspray, especially on windy days. Previously unpainted or chalky surfaces also absorb more on the first coat, so lean toward the lower end of the coverage range when painting bare or weathered material.
How Many Gallons for Common House Sizes
Every house is different, but these ranges hold for typical layouts with average window and door counts, painted with two coats on the body of the house.
| House Size | Typical Wall Area | Gallons (2 coats) |
|---|---|---|
| 1,000 sq ft ranch | 900-1,100 sq ft | 4-6 gallons |
| 1,500 sq ft single-story | 1,200-1,500 sq ft | 6-8 gallons |
| 2,000 sq ft two-story | 1,700-2,100 sq ft | 8-12 gallons |
| 2,500 sq ft two-story | 2,100-2,600 sq ft | 10-14 gallons |
Add one to three gallons of trim paint on top of these numbers for fascia, soffits, window casings, and door frames. If you are changing color dramatically — dark to light or light to dark — budget for a tinted primer coat or an extra coat of finish paint.
Paint vs Stain for Siding
On wood siding you have a choice between paint and stain, and they behave very differently. Paint forms a film on top of the wood, which gives you the widest color selection and the best protection against UV and moisture — but when it fails, it peels, and repainting means scraping and sanding. Stain soaks into the wood, so it fades gracefully instead of peeling, and recoating is as simple as cleaning and applying another coat. Solid-color stains look nearly like paint, while semi-transparent stains let the wood grain show through. Stain generally needs recoating more often (every 3 to 7 years versus 8 to 12 for quality paint), but each recoat is far less labor. If you are leaning toward stain, use our stain calculator to estimate quantities — stain coverage rates differ from paint.
Tips for a Long-Lasting Exterior Paint Job
- Paint in the right temperature window. Apply exterior paint between 50 and 85 degrees Fahrenheit. Below 50, most latex paints will not cure properly; above 85, paint dries too fast and shows lap marks.
- Avoid painting in direct sun. Follow the shade around the house. Paint applied to a sun-baked wall skins over before it can level and bond, leading to blistering and poor adhesion.
- Apply two thin coats, not one thick one. Two thin coats bond and cure better, cover more evenly, and build a more durable film than a single heavy coat.
- Prep is most of the job. Wash the siding, scrape and sand loose paint, caulk gaps, and spot-prime bare wood. Paint fails at poorly prepped spots first.
- Buy quality paint. A premium 100 percent acrylic exterior paint lasts 8 to 12 years, while bargain paint may need redoing in 4 to 5. The labor is the same either way, so better paint is the cheapest upgrade you can make.
- Box your gallons. Mix all your gallons together in a large bucket before starting so slight tint variations between cans never show on the wall.
Frequently Asked Questions
Plan on 8 to 12 gallons for two coats on a typical 2,000 square foot two-story house, depending on surface texture and how many doors and windows break up the walls. Smooth siding lands near the low end; stucco or brick pushes you toward the high end. Add 1 to 2 gallons of trim paint on top.
Prime bare wood, repaired areas, chalky surfaces, and any time you are making a dramatic color change. If you are repainting sound, previously painted siding in a similar color, a separate primer coat is usually unnecessary — just spot-prime scraped or sanded areas before the finish coats.
Quality exterior paint lasts 7 to 12 years depending on climate, sun exposure, and how well the surface was prepped. Harsh sun, coastal salt air, and freeze-thaw cycles shorten the life; thorough prep and premium 100 percent acrylic paint extend it.
Yes, as long as the existing paint is sound. Scrape and sand any loose, peeling, or blistered areas, wash the siding to remove dirt and chalk, caulk gaps, and prime bare spots. New paint applied over failing paint will peel along with it.