Deck Stain Calculator

Stain needed = (deck area × number of coats) ÷ coverage per gallon, rounded up. For a 12 ft × 16 ft (3.6 m × 4.9 m) deck (192 sq ft / 17.8 m²) with semi-transparent stain on smooth wood (300 sq ft per gallon coverage) and 2 coats: 192 × 2 ÷ 300 = 1.28 → 2 gallons. The calculator above adjusts for stain type, wood condition, coats, and any railings or stairs you add.

Stain coverage is the square footage one gallon will cover at one coat. Semi-transparent on smooth wood: 250-400 sq ft per gallon. Solid: 200-300. Oil-based: 150-200. Water-based: 250-400. On rough or weathered wood, coverage drops to about 60% of these numbers because the surface absorbs more product. Always check the can label — manufacturers vary by ±25%. Multiply the area you're staining by the number of coats, then divide by coverage and round up.

Most homeowner jobs use 2 coats. The first coat soaks into the wood and primes it; the second builds the visible finish. Solid stains usually need 2 coats minimum. Semi-transparent often gets by with 1-2 depending on color depth and wood absorbency. Bare or freshly sanded wood may need a third coat to develop full color. Always wait the manufacturer's recommended dry time between coats — 4-24 hours typical.

Manufacturer ranges, smooth wood: Semi-transparent 250-400 sq ft per gallon (most common DIY choice). Solid 200-300 (paint-like, hides grain). Oil-based 150-200 (deepest penetration, most absorbent). Water-based 250-400 (low-VOC, fast dry). On rough or weathered wood, all numbers drop to 100-200 sq ft per gallon. The reference table on this page gives the full grid. Pick a midpoint for estimating; always confirm against the actual can label.

Yes — railings and stairs add significant surface area you'll be staining. A typical spindled railing is about 4 sq ft (0.37 m²) of stain surface per linear foot — top rail, bottom rail, spindles on both sides. Each deck step adds about 6 sq ft (0.56 m²) — tread top, riser face, stringer sides. For a 12 × 16 ft deck with 40 linear ft of railing and 5 stair steps, the railings alone add 160 sq ft and the stairs add 30 — that's an extra 190 sq ft on top of the 192 sq ft deck surface. Use the toggles in the calculator to include them.

Oil-based penetrates deeper into the wood, lasts 3-5 years, hides minor surface flaws, and accepts pigments well — but has high VOCs, takes 24+ hours to dry, and is restricted in some states. Water-based dries in 2-4 hours, has low VOCs, cleans up with soap and water, lasts 2-3 years, and shows surface defects more clearly. Water-based is the dominant new-deck choice; oil-based is preferred for high-traffic decks and older weathered wood that needs deeper penetration. Coverage is similar.

Manufacturer-specific, but typical guidelines: water-based stain 4-6 hours; oil-based 12-24 hours. Wait until the first coat is touch-dry but not fully cured. Don't apply a second coat in direct sun or above 90°F (32°C) — premature drying causes lap marks. Don't apply after recent rain or with rain in the next 24-hour forecast. Most stain failures come from rushing the dry time or applying in poor weather.

Mid-spring through early fall, when temperatures stay between 50°F (10°C) and 90°F (32°C) day and night, with low humidity and no rain forecast for 24-48 hours. Avoid direct full-sun staining (causes lap marks) and morning dew. Brand-new pressure-treated wood needs 4-8 weeks of weather exposure to dry out before staining — fresh PT lumber is too wet to absorb stain. Fall is ideal: cooler temps, lower sun angle, fewer bugs landing in wet stain.

DIY for a 192 sq ft (17.8 m²) deck: 2 gallons of mid-range stain at $40-50/gal = $80-100, plus brushes, rollers, drop cloths, sandpaper for prep ≈ $30. Total $110-130. Pro labor adds $200-500 depending on prep time (power-washing, sanding, repairs) and complexity. Larger decks scale linearly: figure $0.50-$1 per sq ft DIY, $1.50-$3 per sq ft pro. Premium stains (Behr Premium, Cabot Australian Timber Oil) run $60-80 per gallon.

Yes — pick Metric in the unit selector at the top and inputs switch to meters and m². Coverage rates also convert: semi-transparent on smooth wood ≈ 6.1-9.8 m² per gallon (US gallons are still gallons in metric mode since stain is sold by the gallon globally). Total surface area outputs in m². Common conversions: 12 × 16 ft deck = 3.6 × 4.9 m = 17.8 m². Your unit choice persists across pages and tabs via localStorage.