Exterior Paint Calculator
Exterior paint jobs eat gallons fast once you factor in two coats and textured siding. This calculator turns your wall dimensions into an exact gallon and can count so you don’t run short mid-job.
Prefilled from the selected product — adjust to match your can label or surface porosity.
Covers spills, absorption, and touch-ups. 10–15% is normal.
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Application tips
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Coverage & coats
Product profile
Exterior paint gallons come from wall area (length times height) multiplied by the number of coats, then divided by the coverage rate for your chosen paint, usually 300-400 sq ft per gallon depending on surface texture. A waste percentage is added for overspray, cutting in around trim, and touch-ups, and the total is rounded up to whole cans.
Exterior paint coverage by surface type
Coverage rates vary by paint sheen and how textured the siding is. Rougher surfaces soak up more paint per coat.
| Paint Type | Coverage per Gallon | Best For |
|---|---|---|
| Flat exterior acrylic | 350 sq ft | Stucco and rough siding |
| Satin exterior acrylic | 375 sq ft | Wood, vinyl, and fiber-cement siding |
| Solid color exterior stain | 300 sq ft | Cedar and wood siding |
How to calculate exterior paint gallons
- Measure the total length of exterior walls and average wall height.
- Multiply length by height to get total wall area in square feet.
- Factor in coats most exterior jobs need 2 coats for full coverage and color-hide.
- Divide by coverage using the coverage rate for your chosen paint and surface texture.
- Round up to cans since paint is sold in whole gallon or 5-gallon units.
Worked example
Here’s the math for 160 ft of 9 ft siding, 2 coats of satin exterior acrylic.
- Wall dimensions160 x 9 ft
- Area1,440 sq ft
- Coats2
- Coverage rate375 sq ft per gallon
- Waste added8%
- Paint needed8.29 gallons
- Cans (1-gal)9 cans
- Total cost$405
Prep and weather windows matter as much as gallons
Bare wood, patched areas, and stains need a separate primer coat, which isn’t part of the topcoat gallon count above, so budget for it if your siding needs spot-priming or a full prime coat after a color change. Exterior paint also needs the right weather window to cure: most acrylics want surface temperatures between 50-85 degrees F, low humidity, and no rain in the forecast for at least 24 hours after application. Painting outside that window is the most common reason exterior paint peels or blisters within a year or two.
Common mistakes
- Only budgeting for one coatmost exterior colors, especially color changes, need 2 full coats to hide the old color and resist UV fading evenly.
- Ignoring surface texturestucco, brick, and rough-sawn siding soak up more paint than smooth siding – use the lower coverage rate for textured surfaces.
- Skipping primer on bare or patched woodbare wood, patched areas, and stains need a separate primer coat, which isn’t included in the topcoat gallon count.
- Painting outside the temperature windowmost exterior paints need surface temps between 50-85 degrees F and no rain for 24 hours to cure properly.
What this calculator assumes
Adjust your result if your project differs from these.
- Wall area is calculated as total length times average height, before deducting doors and windows.
- Two coats is the default for full color coverage and UV protection.
- Coverage rates assume a properly prepared, primed surface.
- Waste percentage covers overspray, trim cutting-in, and touch-ups.
- Paint is purchased in whole gallon cans; 5-gallon buckets can be substituted for larger jobs.
Common questions
How many coats of paint does exterior siding need?
Two coats is standard for most exterior jobs, especially with a color change; one coat can work for same-color touch-ups on paint that’s still in good condition.
Does stucco need more paint than wood siding?
Yes, textured surfaces like stucco and rough-sawn wood absorb more paint – figure roughly 300-350 sq ft per gallon versus 375-400 for smooth siding.
Should I buy 5-gallon buckets instead of 1-gallon cans?
For jobs over about 15-20 gallons, 5-gallon buckets are usually cheaper per gallon and mean less color-matching between containers.
Do I need to subtract windows and doors from the area?
For rough estimating most contractors skip small deductions since trim work uses roughly the same paint the wall area would have needed.
What temperature is too cold to paint exterior siding?
Most acrylic exterior paints shouldn’t be applied below 50 degrees F, and some formulas need mid-day application in cool weather to fully cure before nightfall.
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Exterior Paint Calculator Estimate
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Project
| Shape | — |
| Dimensions | — |
| Area | — |
| Product | — |
| Coverage | — |
| Coats | — |
| Overage allowance | — |
Shopping list
| Total product | — |
| Cans needed | — |
| Estimated total cost | — |
Notes
Estimate generated by materialcalculate.com. Confirm quantities and coverage with your product label before ordering.