DECK STAIN

Enter your deck length and width in feet. For an L-shaped or wraparound deck, use the L-shape toggle and enter the cutout. Add the railing perimeter in feet — every linear foot of railing has roughly 4 ft² of stain surface (top rail, bottom rail, both faces of balusters). Forgetting the railing is the #1 reason DIYers run out of stain mid-project.

Set the number of coats — 2 is standard for new applications; 1 may suffice for refresh stains over an existing coat. Pick the wood condition: smooth/sealed wood gets 250 ft²/gal coverage; weathered/rough wood drops to 150 ft²/gal because the open grain absorbs much more. The calculator returns gallons rounded up since stain is sold by the gallon.

For a 16 × 12 ft deck with 30 ft of railing, 2 coats, smooth condition:

Deck area = 16 × 12 = 192 ft². Railing area = 30 × 4 = 120 ft². Total = 312 ft². With 2 coats: 624 ft² to cover. At 250 ft²/gal: 2.5 gallons → round up to 3 gallons.

Notice the railing accounts for 38% of the total surface — that's why running out of stain on a deck job is so common when you only stain the deck itself first.

At $30–$60 per gallon for a quality semi-transparent stain, materials run $90–$180 for this deck. For a weathered deck of the same size, drop coverage to 150 ft²/gal: 624 ÷ 150 = 4.16 → 5 gallons ($150–$300). Always do a small test patch first — stain color shifts dramatically based on the wood species and existing weathering.

Skipping the surface prep. Stain doesn't bond to dirty, mossy, or oxidized wood. Wash with deck cleaner (or a 50/50 bleach-water mix) and let dry 48 hours before staining. For weathered decks, sand with 60–80 grit before cleaning.

Staining when the wood is wet or before rain. Stain needs 24–48 hours dry weather to cure. Check the forecast — a sudden rain in the first 12 hours strips the stain right off.

Using the wrong stain type. Solid stains last longest (5–7 years) but obscure wood grain. Semi-transparent shows grain and lasts 2–4 years. Clear sealers last 1–2 years and barely change appearance. Match the stain type to how often you're willing to recoat.

Staining between deck boards. Stain dripping into the gaps between boards never fully cures and remains tacky. Use a brush to wipe excess from the edges, or accept that some drip is inevitable and set up dropcloths under the deck.

Smooth/sealed wood: 250 ft²/gal. Weathered/rough wood: 150 ft²/gal. Always do 2 coats on new applications.

Railing area = roughly 4 ft² per linear foot of railing. Add this to deck floor area before sizing stain.

Solid stains last 5–7 years. Semi-transparent: 2–4 years. Sealers/clear: 1–2 years.

Apply at 50–90°F, in dry weather with no rain forecast for 48 hours.

A 16 × 12 deck takes a single person about 4–6 hours including prep. Two people can knock it out in an afternoon.