Deck Stain and Sealer: How Many Gallons for a 12 x 16 Deck?
October 29, 2026
Deck stain and sealer coverage varies much more than paint coverage, because wood absorbs a lot of finish, especially when it is old, weathered, or rough. Manufacturers list coverage of 150 to 300 square feet per gallon for one coat, with new smooth wood at the high end and aged, rough, or pressure-treated lumber at the low end. Always check the can, and plan for at least two coats if the product calls for it, or one thin coat for semi-transparent finishes.
A 12 by 16 foot deck has 192 square feet of floor. Add railings, balusters, and stairs, which can add 40% or more: a 28-foot railing run that is 3 feet high comes to roughly 84 square feet of surface (counting one face). A total of 276 square feet is realistic.
Skip the math and get your answer instantly:
Open the Deck Calculator →Measuring the Surface
Floor area = length × width. Railing area = linear feet × height × number of faces treated (usually 2), adjusting for balusters, which have more surface than a solid panel suggests: a simple method is to count the railing as a solid panel of the same height on each side. Stairs: treads plus risers (each tread ~ 3 ft × 1 ft = 3 sq ft; each riser 3 × 0.6 = 1.8 sq ft). Add post surfaces. For the example: deck floor 192 + railing 84 (28 ft × 3 ft × 1 face) = 276 sq ft. The sides of the deck's joists and fascia, if stained, add more.
Two coats double the area you need to cover.
| Coverage per gallon (one coat) | Gallons for 276 sq ft, one coat | Gallons, two coats |
|---|---|---|
| 300 sq ft (new smooth wood) | 0.9 | 1.8 |
| 250 sq ft (typical) | 1.1 | 2.2 |
| 200 sq ft (weathered) | 1.4 | 2.8 |
| 150 sq ft (rough, old, thirsty) | 1.8 | 3.7 |
Choosing a Finish
Clear sealers protect from water but give little UV protection, so the wood turns gray. Toners and semi-transparent stains show the grain and contain pigments that block UV, lasting 2 to 3 years on horizontal surfaces. Solid stains hide grain, last 3 to 5 years, and behave like thin paint. Oil-based finishes penetrate wood and resist water, whereas water-based formulas dry faster, clean up with water, and have lower odor. New pressure-treated wood often needs to dry for a few weeks to months before staining; test by sprinkling water: if it beads, wait; if it soaks in, it is ready.
Preparation and Application
Clean the deck with a deck cleaner or wood brightener, scrub off mildew and old finish, and rinse. Let the wood dry for at least 24 to 48 hours. Sand rough spots, and replace loose boards and rusted fasteners. Apply stain in the shade, in temperatures between 50 and 90 degrees Fahrenheit, with no rain expected for 24 hours. Work along the grain, brush into the gaps, and avoid puddles and lap marks by staining a few boards at a time from end to end. Back-brushing after spraying forces the finish into the wood. Keep a wet edge. Wipe off excess after 15 minutes when using penetrating stains.
Cost and Maintenance
Stain costs roughly $30 to $70 per gallon. For a typical deck, materials of $100 to $250 plus rental of a sprayer or pressure washer are common, while hiring a professional costs $2 to $5 per square foot. Re-coat when water no longer beads on the surface: sprinkle water on the deck annually. Regular sweeping and cleaning extend the life of the finish. Keep a note of the product and color for touch-ups.
Frequently Asked Questions
How much stain do I need for a 12x16 deck?
About 2 to 4 gallons for two coats, depending on the wood and the product, if railings and stairs are included.
How many square feet does a gallon of deck stain cover?
Typically 150 to 300 square feet per coat.
How long should new pressure-treated wood dry before staining?
Often weeks to months. Test with water: if it soaks in, it is ready.
Does the deck need two coats?
Follow the label; semi-transparent stains often need one coat, solid stains two.
How often should I re-stain?
Every 2 to 5 years depending on the product and exposure.