How Much Deck Stain Do I Need?
Quick answer: count deck top + board sides + railings — a gallon of semi-transparent stain covers 250–300 sq ft per coat. A 12×12 deck with railings totals ~300–400 sq ft, so plan 2 gallons per coat, 4 gallons for two coats.
- What counts as stained surface
- Coverage by stain type
- How many coats
- Worked example: 12×12 deck
- Common mistakes
- FAQ
What counts as stained surface
Staining a deck covers more than the top: the board sides (the exposed edges between gaps) add roughly 25% to the top area, and railings add about 1/3 of the top area on a typical deck. If your deck is at ground level with no railings, skip the railing term. For stairs, count the treads and risers like extra deck area.
Coverage by stain type
| Stain type | Coverage per gallon | Notes |
|---|---|---|
| Semi-transparent | 250–300 sq ft | Most common, shows wood grain |
| Solid | 150–200 sq ft | Paint-like film, hides grain |
| Transparent | 300–350 sq ft | Thin, needs more frequent re-coats |
| Weathered wood | ~200 sq ft | Porous wood drinks the first coat |
How many coats
Two coats on new or bare wood — the first soaks in, the second builds the protective film. A previously stained deck usually needs one coat, unless you're changing color or the finish is worn through. Rough or weathered wood eats the first coat, so count the full coverage per coat and don't stretch a gallon.
Worked example: a 12×12 deck with railings
- Deck top: 12 × 12 = 144 sq ft
- Board sides: +25% = 36 sq ft
- Railings: +33% = 48 sq ft
- Total ≈ 228 sq ft → 1 gallon per coat, 2 gallons for two coats (semi-transparent)
Add a third gallon if the wood is weathered and porous — the first coat will vanish into the grain.
Common mistakes
- Staining only the top. The exposed board edges and railings are the first to fail — they must be covered too.
- One coat on bare wood. New decks need two coats; one leaves the wood unprotected in a season.
- Stretching a gallon on rough wood. Weathered surfaces absorb 30–50% more. Buy the extra can up front.
- Staining wet or freshly cleaned wood. Stain needs wood at ~15% moisture or less, and at least 24 hours after pressure washing.
FAQ
Count the deck top, the board sides, and the railing separately: a gallon of semi-transparent stain covers 250–300 sq ft for one coat. A 12×12 deck with railings needs about 2 gallons per coat — plan 4 gallons for two coats.
About 250–300 sq ft per gallon for semi-transparent stain on one coat, 150–200 sq ft for solid stains. Rough or weathered wood absorbs more — drop the estimate to 200 sq ft per gallon.
A 12×12 deck surface is 144 sq ft; add the board sides (roughly +25%) and railings. Total is about 300–400 sq ft, which takes 1.5–2 gallons per coat — about 4 gallons for two coats.
Two coats on new or bare wood — the first soaks in, the second builds the film. Repainting a stained deck usually needs one coat, unless the color is changing or the finish is worn through.
Estimate the railing as about 1/3 of the deck top area, or measure each baluster and rail by hand. A baluster (2×2×36 in) is about 1.5 sq ft including all four sides.