Deck Stain Quantity Calculator
Buying too little deck stain means a second trip mid-project and a risk of color mismatch between cans, while buying too much wastes money on product that dries out before the next season. This deck stain calculator works out how many gallons you need from three numbers: the deck area in square feet, the coverage rating the stain manufacturer prints on the can, and the number of coats you plan to apply. Coverage varies widely because a smooth, previously sealed board soaks up far less stain than rough or weathered wood, so always read the figure on your specific product. Most deck stains cover somewhere between 200 and 400 square feet per gallon per coat. Every figure here is computed deterministically from your inputs, so the same deck and coverage always return the same quantity. Enter your measurements below to size a stain order before you start, compare one-coat and two-coat finishes, or check whether a partial can left from last year will be enough, with a worked example that reconciles exactly to the calculator defaults so you can follow each step. Round up to whole cans when you buy so you are never caught short partway through the job.
Gallons of stain equal the deck area multiplied by the number of coats, divided by the coverage per gallon. A 200 sq ft deck at 250 sq ft per gallon coverage with 2 coats needs 1.60 gallons of stain.
Deck stain formula
gallons = (deck area x number of coats) / coverage per gallon
deck area in square feet, coverage in square feet per gallon per coat
Multiplying the deck area by the number of coats gives the total area the stain must cover. Dividing by the coverage per gallon gives the gallons required. Round up to whole cans when buying.
Worked example
Take a deck of 200 square feet, a stain rated at 250 square feet per gallon, applied in 2 coats.
- Total area to cover: 200 x 2 = 400 sq ft
- Gallons needed: 400 / 250 = 1.60 gallons
You need 1.60 gallons of stain, which matches the calculator's default inputs exactly. In practice you would buy 2 gallons to allow for waste and touch-ups.
Deck Stain Quantity Calculator: frequently asked questions
How do I find my deck area?
Multiply the deck length by its width in feet. For an irregular deck, split it into rectangles, calculate each area, and add them together. Include stairs and railings separately if you plan to stain them, as they add surface area.
How many coats of stain do I need?
Many deck stains are designed for a single coat, but bare or thirsty wood and some semi-transparent products call for two. Follow the manufacturer's instructions, and set the number of coats in the calculator to match the finish you want.
Why does coverage vary so much?
Rough, weathered, or bare wood absorbs much more stain than smooth, previously sealed boards, so the same can may cover 200 square feet on old wood and 400 on new. Always use the coverage figure printed on your specific stain for the most accurate estimate.
Should I buy extra stain?
Yes. Round up to whole cans and add a little for waste, spills, and future touch-ups. Buying all your stain at once from the same batch also avoids slight color differences between cans, which can show on a large deck.
Does this include the railings and stairs?
Only if you include their area in the deck area input. Railings, balusters, and stair treads add a surprising amount of surface area, so measure or estimate them and add to the total if you intend to stain them.
Official sources
- Measurement, units and dimensional standards: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.