How Much Paint for a Deck?
Deck floor plus railings. The railings are what most estimates forget.
A 12x16 deck needs 2 gallons of stain for two coats on the floor alone. Add railings and you need roughly one more gallon. So a realistic budget for a 12x16 deck with railings is 3 gallons.
Estimates only. Textured walls, high ceilings, sprayers and major colour changes can all increase the amount you need. Always buy slightly more than the calculation suggests.
Stain needed by deck size
| Room / surface | Surface | Coats | Paint | Paint cost |
|---|---|---|---|---|
| Small deck, 10x10 floor, 2 coats | 100 sq ft | 2 | 1 gal | $42 |
| Small deck, 10x10 with railings | 140 sq ft | 2 | 2 gal | $84 |
| Standard deck, 12x16 floor, 2 coats | 192 sq ft | 2 | 2 gal | $84 |
| Standard deck, 12x16 with railings | 270 sq ft | 2 | 3 gal | $126 |
| Large deck, 16x20 with railings | 448 sq ft | 2 | 4 gal | $168 |
| Standard deck, 12x16, one coat | 192 sq ft | 1 | 1 gal | $42 |
Floor only, at 250 sq ft per gallon for weathered deck boards. Add 30-40 % for railings and stairs.
Working out deck surface area
The floor is straightforward: length × width. A 12x16 deck is 192 square feet.
The railings are the part people forget. A railing system has a top rail, a bottom rail and balusters, and all of it needs coating. A rough rule that works well in practice is to add 30 to 40 % to the floor area for a typical railing, and more if there are steps.
If you want to be precise, measure the linear feet of railing and multiply by about 3 square feet per linear foot for a standard railing with balusters.
New wood versus old wood
Deck boards are the classic worst case for paint absorption, because they are outdoors, weathered and full of end grain.
- New, untreated or pressure-treated wood: this is the thirstiest surface you will ever coat. Pressure-treated wood should also be left to dry for weeks or months before finishing, and it can absorb as little as 150 sq ft per gallon on the first coat.
- Previously stained deck: 300-350 sq ft per gallon if the old finish is sound.
- Weathered, grey, dry boards: 200-250 sq ft per gallon.
When in doubt, use 200. Overshooting by a gallon is far cheaper than a half-finished deck with an obvious line across it.
Water-based or oil-based?
Water-based stains dry faster, have lower odour, clean up with water, and are the modern default. They typically need two coats and last two to three years before refreshing.
Oil-based stains penetrate deeper and last longer — often three to five years — but they smell strongly, need solvent cleanup, and are increasingly restricted in some states.
Whichever you choose, the preparation matters more than the product. A deck must be clean, dry and free of mill glaze before any finish goes on. New boards often have a mill glaze that prevents penetration, and it needs to be broken with a light sanding or a chemical etcher.
Frequently asked questions
How much stain for a 12x16 deck?
About 2 gallons for two coats on the floor alone, or 3 gallons if you include the railings. Weathered boards can push this higher.
Do I need one coat or two on a deck?
Two coats on new, bare or weathered wood. One coat is enough only when refreshing a deck that was finished recently and is still in good condition.
How long should I wait before staining a new deck?
For pressure-treated wood, wait until it has dried out — often several weeks to a few months. Sprinkling water on the boards is a good test: if it soaks in, the wood is ready; if it beads, it is not.
Can I use the same product on the deck and the railings?
Yes, and you should, for a consistent colour. Just remember the railings add roughly 30-40 % to the total surface area.