How this calculator works. Deck area = length × width. Railings = linear feet × 3.5 sq ft per foot — the standard estimating figure that accounts for top rail, bottom rail, and both sides of the spindles. Steps count ≈9 sq ft each (tread + riser + ends). Total is divided by your coverage rate.
Coverage defaults follow typical manufacturer labels for semi-transparent stain: 250 sq ft/gal on sealed smooth wood, 150 sq ft/gal on new, rough-sawn, or weathered thirsty wood, which drinks nearly double.
How much stain does a deck take?
Stain coverage varies more than any other coating because wood, not the product, decides absorption. The same gallon covers 250 square feet of smooth sealed cedar or barely 150 of weathered, thirsty pine. When in doubt, use the thirsty number — leftover stain keeps for next year's touch-up; running out mid-deck leaves a visible lap line across your first board.
Railings are the hidden area everyone underestimates: a spindled railing has a top rail, bottom rail, and dozens of 4-sided balusters. The trade's 3.5-sq-ft-per-linear-foot figure looks like an overestimate until you're on your knees with a brush wondering where the stain went.
Coverage by product type
| Product | Typical coverage/gal | Coats |
|---|---|---|
| Clear sealer / toner | 250–300 sq ft | 1 |
| Semi-transparent stain | 150–250 sq ft | 1–2 |
| Solid stain (paint-like) | 150–200 sq ft | 2 |
Buying tips
Semi-transparent stains apply in one coat on most wood — a second coat only if the wood absorbs the first within minutes. Solid stains behave like paint and want two. Whatever you buy, box the cans (mix them together in a bucket) before starting: tint varies can to can, and a deck shows it.
Common questions
New pressure-treated deck — stain now or wait?
Wait until water stops beading on the surface — usually 1–6 months after installation depending on how wet the lumber arrived. The sprinkle test: if droplets soak in within a minute, it's ready.
Do I need to strip the old stain?
Going darker or same tone with the same type (e.g., semi-transparent over faded semi-transparent): clean and re-coat. Changing type or going lighter: strip or sand. Solid stain over peeling solid stain just peels faster.
One gallon or the 5-gallon pail?
Pails run ~20% cheaper per gallon. If your total is 4+ gallons, buy the pail — and you get pre-boxed consistent color as a bonus.
Stain the underside of boards?
No need for looks, but sealing cut ends and the first foot near the ground meaningfully slows rot. If the deck is low to damp ground, a sealer coat underneath (before installation) is the real fix.