How Much Paint for House Exterior: 5 Quick Estimates: Practical checks and tricks I use to calculate paint needed for an exterior — plus budget and color tips

I once showed up to a job with a ladder, brushes, and exactly zero idea how much paint the client had ordered — she thought two gallons would cover a whole Victorian. We laughed, then I taught her a quick trick to "visualize colors in 3D" so she could see the result before we bought a single can. That little misadventure taught me that measuring well and previewing color saves time and money.

1. Measure wall area like a pro

I always start by measuring linear feet and heights: length × height for each wall, then add gables or dormers. It’s simple math but easy to mess up on complex roofs; multiply total square footage by the number of coats you plan to apply to get gross square feet to cover.

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2. Subtract doors, windows, and non-painted surfaces

Doors and windows eat up paintable area — subtract roughly 20–50 sq ft per large opening depending on the style. The upside is that trimming and accents often use different paint, so this step helps you order exact gallons for body vs. trim.

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3. Know paint coverage per gallon and primer needs

Most exterior paints list coverage on the can — a typical range is 250–400 sq ft per gallon depending on surface texture and porosity. If you’re dealing with raw wood, new siding, or drastic color changes, factor in a primer coat; primers often cover similarly but sometimes less on rough surfaces, which means more material and budget.

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4. Plan coats, weather windows, and wastage

I always plan for two finish coats plus primer when needed; that’s the best insurance for durability. Also allow 10–15% extra for waste, touch-ups, and absorption — better to have a spare quart than to run out on a windy afternoon.

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5. Visualize, buy smart, and store leftovers

Before ordering, I like to test samples on different walls and view them in morning and evening light — small samples can save repaints. Buy full gallons for the main color and quarts for accents, and seal leftovers tightly; labeled cans are lifesavers years later for repairs.

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Quick practical checklist

Measure exterior wall area, subtract openings, multiply by coats, divide by paint coverage per gallon, then add 10–15% extra. If you prefer a digital assist, I often recommend tools that help you create precise plans so your quantities are accurate.

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FAQ

1. How do I calculate how many gallons I need?

I multiply total paintable square footage by the number of coats, then divide by the paint’s stated coverage per gallon. Add 10–15% for waste and touch-ups.

2. How much does one gallon of exterior paint cover?

Coverage varies, but many exterior paints cover about 250–400 sq ft per gallon on smooth surfaces; rough or porous siding reduces that number.

3. Do I need primer for exterior painting?

If you’re painting new wood, raw siding, or making a drastic color change, primer is highly recommended and can increase overall paint adhesion and longevity.

4. How many coats are usually required?

Most exterior jobs use one coat of primer and two finish coats of topcoat for best durability and uniform appearance; some high-hide paints may reduce this to two total coats.

5. What about trim and doors?

Trim and doors often need different paint types (satin or semi-gloss) and less surface area, so buy quarts or dedicated trim gallons to avoid waste.

6. Can I estimate paint needs from photos?

Photos help with color choice but aren’t precise for quantities; accurate linear and height measurements remain the most reliable method.

7. Where can I find paint coverage specs?

Manufacturers publish technical data sheets with coverage numbers — for example, Sherwin-Williams lists typical coverage rates per gallon on their technical pages, which are helpful for planning (Sherwin-Williams technical data).

8. Any tips for leftovers and touch-ups?

Label leftover cans with location and date, store upright in a cool, dry place, and use a tight lid seal or transfer to smaller containers for long-term storage.

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