Deck stain coverage varies far more than wall paint, because both the stain type and the thirst of the wood change how far a gallon goes. Measure carefully, count the parts people forget, and read the can, because a generic figure will let you down here.
Measure the whole deck, not just the floor
Start with the deck floor area, length times width. Then add the parts that quietly add up: the railings, the balusters or spindles, the stair treads and risers, and the fascia boards around the edge. On a deck with a lot of railing, these can add a third again to the floor area, so do not estimate from the floor alone.
Coverage varies by stain
Transparent and semi transparent stains soak into the wood and cover more area per gallon. Solid stains sit on the surface like paint and cover less. New, rough or weathered wood drinks far more than smooth, previously coated boards. The coverage on the can, often 200 to 400 square feet per gallon, is a starting point and a range, not a promise.
| Stain type | Typical coverage per gallon |
|---|---|
| Transparent and semi transparent | 250 to 400 sq ft |
| Semi solid | 200 to 350 sq ft |
| Solid | 200 to 300 sq ft |
New wood drinks more
Fresh, bare or pressure treated wood that has weathered absorbs much more on the first coat than a deck that already carries a finish. A first time finish on new timber can use noticeably more than the can suggests, so lean toward the lower end of the coverage range and buy a margin.
Coats
Most deck stains call for one to two coats. Bare or thirsty wood often needs two. Buy enough for the planned coats plus a margin, because mixing a fresh can mid project risks a visible colour shift between batches, especially with semi transparent stains. If you must use more than one can, box them, meaning combine and stir them together, for a consistent colour.
Conditions matter
Stain goes on best on dry wood, out of direct hot sun, with no rain forecast for a day or two. Applying to damp wood or in the heat affects both how it absorbs and how far it goes, which throws off your estimate as well as the finish. A stain that dries too fast in the sun will not penetrate properly and can leave lap marks.