Paint Coverage Calculator
Planning a painting project? Use this free paint coverage calculator to estimate how many gallons of paint you need based on your total square footage, number of coats, and the coverage rate of your paint. This tool helps you avoid buying too much—or worse—running out of paint halfway through the job.
Just enter the area you plan to paint, and the calculator will show you exactly how much paint to buy, so you can budget accurately and make one trip to the store.
About This Paint Coverage Calculator
This paint coverage calculator helps you estimate exactly how much paint you need for your project based on room dimensions, square footage, number of coats, and paint coverage per gallon. It also allows you to subtract windows and doors for a more accurate result – a feature many basic calculators leave out.
Most interior paints cover around 300–400 sq ft per gallon, but coverage can vary depending on wall texture, primer usage, paint brand, and color contrast. This tool lets you keep the industry standard 350 sq ft or customize it for your paint brand.
Planning multiple rooms or a full home repaint? Simply click “Add another room” and the calculator will total everything for you automatically.
Working on a full renovation? You may also want to use our Custom Flooring Calculator to eestimate how many boxes you need, including a waste allowance for cuts and patterns. Enter room dimensions and your tile/plank size to get an instant quantity and cost estimate.
Frequently Asked Questions
How many square feet does one gallon of paint cover?
On average, a gallon of interior paint covers 350 sq ft with one coat. Rough surfaces like textured walls or unprimed drywall may only cover 250–300 sq ft. Smooth, primed surfaces can reach 400 sq ft per gallon.
Do I really need two coats of paint?
For most walls, two coats provide better color coverage, durability, and a smooth finish. If you're painting a darker color over a light wall (or vice versa), two coats are highly recommended. Bold colors like navy, red, or black almost always need two coats or a primer layer.
How much paint should I buy for windows and doors?
A standard interior window is around 15 sq ft, and a door is around 20 sq ft. This calculator automatically subtracts those areas so you don’t overbuy. Just expand the Advanced Options section to enter how many you have.
Should I buy extra paint for touch-ups?
Yes — professionals recommend buying an extra 10% for future touch-ups and surface absorption. This calculator includes that buffer for you and even breaks down how many gallons + quarts to buy for the most cost-efficient purchase.
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