Exterior Paint Calculator – How Much Paint You Need
Nothing freshens up a home quite like a new coat of paint on the outside.
Enter up to 4 walls. Leave any wall you do not need blank (0). Measure length × height in feet.
Based on coverage of 350 sq ft per gallon. Gallons are rounded up to the nearest quarter gallon so you do not run short. Rough or unpainted surfaces may need extra paint.
It boosts kerb appeal, protects your walls from rain and sun, and makes the whole house feel loved again.
But before you pick up a brush, there is one question every homeowner asks: how much paint do I actually need?
Buy too little and you are back at the store mid-project with a half-painted wall. Buy too much and you have expensive cans gathering dust in the garage.
That is where this free exterior paint calculator comes in. Measure your walls, tell us how many coats you plan, and it works out the gallons for you.
It rounds up so you never run short, plus the litres if your paint is sold that way. It takes less than a minute, and it can save you a wasted trip and a wasted can.
Grab a tape measure, jot down your wall sizes, and let us do the maths.
How to Use
Example
Let us say you have one wall that is 10 feet long and 10 feet high, and you plan a single coat.
The wall area is 10 × 10 = 100 square feet. At 350 square feet per gallon, that works out to 100 ÷ 350 = 0.29 gallons.
Since paint is not sold in tiny fractions, the calculator rounds up to the nearest quarter gallon, giving you 0.5 gallons, which is about 1.9 litres.
Now picture a bigger job: four walls of 20 × 10 feet each, with two coats. That is 800 square feet times two coats, or 1,600 square feet of painting.
That needs about 4.57 gallons, rounded up to 4.75 gallons. Rounding up like this means you finish the last wall without a stressful dash to the store.
THE BOTTOM LINE
Painting the outside of your home is one of the best value upgrades you can make, but it starts with buying the right amount.
Too little paint means mismatched batches and wasted weekends, while too much means money sitting in a can.
This calculator keeps it simple: measure your walls, choose your coats, and get a clear answer in gallons and litres, already rounded up so you are covered.
Remember that rough brick, bare wood and very dark colours can drink up more paint than smooth, previously painted walls, so keep a little extra in mind for those.
Plan well, paint on a dry mild day, and enjoy the moment you step back and see your home looking brand new.
Frequently Asked Questions
How much area does one gallon of exterior paint cover?
About 350 square feet in one coat on a smooth surface. Rough surfaces like bare brick can drop to 250 or less, so check your paint can and add a little extra.
Should I subtract windows and doors from my wall area?
You can, but most painters do not bother. The paint you save roughly matches what you need for touch-ups and trim. Keeping the full area gives you a small safety cushion.
Do I really need two coats of exterior paint?
Two coats are almost always worth it outdoors. The first coat grips the surface, the second builds colour and weatherproofing. One coat is enough only when repainting the same colour over paint in good shape.
How do I convert gallons to litres?
One US gallon equals 3.785 litres, and this calculator does it for you. So 4.75 gallons is about 18 litres. Just round up to the nearest can size when you shop.
What affects how much paint I will use?
Surface texture, colour change, and weather matter most. Rough surfaces absorb more paint, dark-to-light needs extra coats, and strong sun dries paint too fast. Primer on bare areas helps too.
How much extra paint should I keep for touch-ups?
Keep at least a small sealed can of your exact paint and colour. The calculator already rounds up, which usually leaves a little spare. Store it cool and dry, with the lid tight.
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