Deck Stain Calculator
Enter your deck size and railing length to get the gallons of stain or sealer to buy, with coats and real-world coverage rates factored in.
Enter 0 if you are only doing the floor. Both sides of a typical railing count as about 3.5 sq ft per linear foot.
Check the can: 150 to 300 for rough or thirsty wood, 250 to 350 for smooth sealed wood.
Gallons to buy
3
Exact need
2.66 gal
Total area
332 sq ft
192 sq ft of floor plus 140 sq ft of railing, times 2 coats. If the exact need is just over a whole gallon, one extra quart-size can may beat rounding up a full gallon.
How the math works
Floor area is length times width. Railings are estimated at 3.5 square feet of stainable surface per linear foot, which accounts for both faces of the top rail, balusters, and posts on a typical 36 inch guardrail.
Total area times coats, divided by your product's coverage rate, gives exact gallons. The buy number rounds up to whole gallons because that is how stain is sold, and leftover stain is what you will want for touch-ups next season anyway.
FAQ
- How much stain do I need for a 12x16 deck?
- A 12 by 16 deck is 192 square feet. At a typical 250 square feet per gallon, one coat takes 0.77 gallons and two coats take about 1.5 gallons, so buy two gallons. Railings add roughly 3.5 square feet per linear foot when you count both sides.
- How many coats of deck stain should I apply?
- Two thin coats for most semi-transparent and solid stains, applied wet-on-wet or per the can's recoat window. One coat is common for penetrating oil sealers on dense or previously coated wood, since extra material that cannot soak in will film and peel.
- Why does coverage vary so much between products?
- Rough-sawn, weathered, or first-time-stained wood drinks far more product than smooth sealed boards. That is why cans list a range like 150 to 300 square feet per gallon. Use the low end for old thirsty decks and the high end for recoats.