Running out of finish mid-project — or buying three gallons too many — both come from guessing coverage. Enter your surface size, product and coats to get the exact amount to buy.
Your surface
How the math works
Gallons needed = (surface area × coats) ÷ coverage per gallon
The result is then translated into what you actually buy at the store: whole gallons plus quarts for the remainder (1 quart = ¼ gallon). Two thin coats almost always look better and use barely more product than one thick coat that drips and peels.
Tips for a finish that lasts
- Stain is not paint. Stain soaks in — the first coat on raw pine can use 30% more than the label rate. Sealed or previously finished wood uses less.
- Never skip the prep math. Coverage assumes a sanded, clean surface; our sanding and finishing guide walks the full process.
- Buy all your finish at once. Batch tints vary slightly between cans and mixing trips — one purchase, one consistent color.
- Fence or deck project? Count the lumber first with the wood fence calculator or deck board calculator, then come back here for the stain.
Frequently asked questions
How much area does one gallon of paint cover?
About 350 sq ft on a smooth, primed surface — roughly one coat on a 12×15 wall area with a bit to spare. Unprimed drywall and rough wood cover less, closer to 300.
How much stain do I need for a deck?
Deck stain covers about 200 sq ft per gallon on the deck surface (less on thirsty, weathered boards — sometimes 150). Don’t forget the railing and step faces; add their area to the floor area, or run this calculator twice.
Do I really need two coats?
For paint and polyurethane, yes — the second coat is where durability and even color come from. Stain is often one coat by design; a second coat darkens rather than protects, so test on scrap first.
How much polyurethane for a tabletop?
A quart covers roughly 125 sq ft — a 3×5 ft tabletop (15 sq ft per coat, both sides more) needs only a few ounces per coat. A single quart handles most furniture projects with plenty left for the next one.