Paint Quantity Calculator
Enter your wall dimensions and coat count, and this calculator tells you exactly how many gallons to buy.
About
About Paint Quantity Calculator
A standard gallon of quality architectural paint covers roughly 350 to 400 square feet with one coat on smooth drywall, a number that shifts meaningfully with wall texture, heavily textured surfaces like stucco or popcorn ceilings have far more actual surface area than their flat square footage suggests, which means they drink up noticeably more paint per wall than a smooth surface does. This calculator applies that coverage rate to your actual measurements so you're not guessing at the paint aisle.
Eyeballing paint needs at the hardware store tends to go one of two ways, buying extra expensive gallons you don't end up using, or running short halfway through an accent wall and having to make a second trip with a possible color-batch mismatch. Measuring your actual wall perimeter and height first, then subtracting doors and windows, avoids both outcomes.
Professional painters almost universally recommend two coats regardless of how good the first coat looks going on, since a single coat rarely achieves full, uniform color opacity or the durability a second coat provides, especially over a different base color.
Enter your room's wall perimeter and ceiling height, then subtract the area of doors and windows. Specify your planned number of coats, and the calculator returns the exact number of gallons needed for the project.
Home renovation plans are personal. The calculation runs entirely in your browser, with no room dimensions transmitted to a server.
FAQ
Frequently asked questions
How much area does one gallon of paint actually cover?
Roughly 350 to 400 square feet with a single coat on smooth drywall, though textured surfaces reduce that coverage since they have more actual surface area than their flat measurement suggests.
Should I always plan for two coats?
Yes, professional painters recommend it almost universally, since a single coat rarely delivers full, even color opacity or the durability that a second coat adds, especially over a different existing color.
How do I account for doors and windows in my total?
A common approach subtracts about 20 square feet per standard door and 15 square feet per average window from your total wall surface area before calculating paint needed.
Does wall texture change how much paint I need?
Yes, textured surfaces like stucco, brick, or popcorn ceilings have significantly more actual surface area than smooth drywall of the same dimensions, requiring extra paint for full coverage.
Do I need primer in addition to paint, and does that change the quantity?
Primer is calculated and purchased separately from paint, typically covering a similar area per gallon, around 300 to 400 square feet. Bare drywall, a major color change, or a stained wall usually needs a dedicated primer coat before the paint coats this calculator estimates.
Why did I run out of paint before finishing, even after calculating the quantity?
Textured walls, dark base colors needing extra coverage, or simply applying paint more thickly than the can's stated coverage rate assumes are the most common reasons. Buying slightly more than the calculated amount, and keeping the receipt for an easy return, avoids a mid-project store run.
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