Paint Calculator
Find out how many gallons of paint you need and estimate the total cost.
How many gallons of paint do I need?
To estimate gallons of paint needed, multiply your total wall area by the number of coats you plan to apply, then divide by how much square footage a single gallon covers (typically 350-400 square feet per coat, as printed on most paint cans). This calculator rounds up to the nearest whole gallon since paint stores sell in full gallon or quart increments, and it's always better to have a little extra than to run short mid-project and risk a slight color mismatch between cans.
Why do most projects need two coats?
A single coat rarely provides even, opaque coverage, especially over a different existing color, a stain, or bare drywall — most professional painters recommend two coats for a uniform, long-lasting finish. Deep or bold colors and drastic color changes (like painting over a dark wall with a light color) sometimes require a tinted primer coat or a third coat of paint to fully cover.
Tips for buying the right amount of paint
Measure wall area by multiplying each wall's height by width and subtracting large windows or doors if you want to be precise, though many painters skip this subtraction since trim work uses leftover paint anyway. Buy from the same batch or "lot number" when possible to avoid subtle color variation, and always keep a small amount of leftover paint for future touch-ups.
Frequently Asked Questions
How much does one gallon of paint cover?
Most standard paint covers 350-400 square feet per gallon per coat, though this can vary with surface texture, paint quality, and application method (roller vs. sprayer). Always check the coverage figure printed on your specific paint can label.
Do I really need two coats of paint?
In most cases, yes. A single coat rarely provides even, opaque coverage, especially over a different existing color. Two coats give a more uniform, durable finish, and drastic color changes may need a primer coat or even a third coat.
Should I subtract windows and doors from my wall area?
You can, but many painters skip this step since leftover paint is typically used for touch-ups, trim, or closets anyway. If you have unusually large windows, doors, or built-ins, subtracting them can slightly reduce the amount of paint you need to buy.
How do I measure wall area for painting?
Measure each wall's height and width, multiply them together, and add up all the walls in the room you're painting. Enter that total square footage into the calculator above along with your desired number of coats.
Do I need primer in addition to paint?
Primer is recommended over bare drywall, stained surfaces, or when making a drastic color change (like light over dark). Many modern "paint and primer in one" products reduce but don't always eliminate the need for a separate primer coat.
How much does a gallon of paint cost?
Paint prices typically range from $25-$80+ per gallon depending on brand and quality, with premium paints costing more but often requiring fewer coats. Adjust the cost-per-gallon field above to match the specific product you're planning to buy.
Should I buy extra paint beyond the calculated amount?
It's a good idea to buy a little extra or keep leftover paint for future touch-ups, since color batches can vary slightly between purchases. This calculator rounds up to the nearest full gallon so you won't come up short mid-project.
How accurate is this paint calculator?
This tool gives a solid planning estimate based on standard coverage rates, but actual paint usage can vary with surface texture, application tool, paint quality, and color. Always check your specific paint can's coverage rating for the most accurate figure.