As an Amazon Associate I earn from qualifying purchases.
Calculate gallons of stain needed.
With these inputs:
| Result | Value |
|---|---|
| Gallons needed | 2 gal |
| Exact amount | 2.0 gal |
| Buy as | 2 × 1 gal |
| Total coverage area | 400 sqft |
| Estimated cost | $84 |
Add ~15% extra for railings and stairs if not already included in your sqft.
Stain coverage on a deck is always worse than the can claims, because the label figure assumes smooth new lumber and a deck is rough, weathered and horizontal. Railing is worse again — both faces plus every baluster. This works out realistic gallon counts from the deck and railing surfaces separately, so you buy once.
Work on about 200 square feet per gallon for semi-transparent stain on weathered decking, not the 300 to 400 on the label. Add two square feet of surface for every linear foot of railing. A 16 by 12 ft deck with 40 ft of railing is 272 square feet of surface — two gallons, and buy the second before you start rather than halfway through.
One for penetrating semi-transparent and toner products — a second coat mostly sits on the surface and peels later. Two for solid stains and deck paints, which are film-forming and depend on film thickness. The exception is very dry, thirsty wood, where the first coat disappears; apply the second while the first is still wet in that case.
A sealer is a clear water repellent that stops water soaking in but offers almost no UV protection, so the wood still greys and it needs redoing every year. A stain adds pigment, and pigment is what blocks UV — that is why the more opaque the product, the longer it lasts. Semi-transparent gets two to three years, solid three to five.
Two clear dry days, out of direct sun, with the temperature between about 50 and 90 degrees. Stain applied to a hot board in full sun flashes off before it penetrates and leaves lap marks. Spring and early autumn are the usual windows. The deck must be dry throughout — not just dry on top — so allow 48 hours after rain or washing.
A 12x16 deck floor is 192 square feet. At about 200 square feet per gallon for one coat of semi-transparent stain on sound wood, that is one gallon for the floor; on weathered wood at about 150 square feet per gallon it is 1.3 gallons. Add roughly two square feet for every linear foot of railing, so 40 ft of railing adds 80 square feet — buy two gallons, or a larger pail for a two-coat product.
Yes. Enter the spread rate printed on your product's label or data sheet as the coverage, and the number of coats the maker specifies. Label figures assume smooth new wood, so on weathered boards use a lower number than the can shows. For Ready Seal's two wet-on-wet coats, follow the Ready Seal section on this page.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.