Deck Stain Calculator
Enter your deck size, wood surface, and number of coats and get the gallons of stain to buy — coverage rounded up to whole cans.
gallons = covered ÷ 200 sq ft/gal → 4 gal
Stain is sold by coverage — how many square feet a gallon spreads — so the math is deck area divided by that coverage, times the number of coats. The catch is that coverage swings widely with the wood. A smooth, previously sealed deck might take a gallon `250` square feet, while rough-sawn, weathered, or bare boards drink it up at closer to `150`. Pick the description that matches your boards and the tool uses the matching rate.
Coats multiply the demand. Two thin coats protect better than one thick one and are the norm for semi-transparent deck stains, so a second coat doubles the area to cover. Multiply deck area by coats, divide by the coverage rate, and round up to whole cans — you cannot buy two-thirds of a gallon, and a little extra covers rails, stairs, and touch-ups the flat area does not include.
Enter your deck's length and width, choose the surface, and set the coats. The tool returns the gallons to buy along with the total area painted. It sizes the field of the deck; add for spindles, stair risers, fascia, and the underside if you are finishing it, and always follow the coverage printed on your specific product — the numbers here are typical ranges, not a guarantee.
covered area = 320 × 2 = 640 sq ft
gallons = 640 ÷ 200 = 3.2 → 4 gallons