Deck stain coverage looks straightforward — a gallon labeled 250 ft² should cover 250 ft². In practice, deck condition, application style, and the railing nobody remembered measuring all push the real number around. Here is the practical version.

Smooth vs weathered — the 100-square-foot gap

The single biggest variable in stain coverage is whether the wood has been previously sealed or has weathered to bare gray:

  • Smooth or recently sealed wood: 250 ft² per gallon. The first coat over a sealed surface sits on top.
  • Weathered or rough wood: 150 ft² per gallon. Open grain soaks in 50-70% more product than smooth.

A 200 ft² deck swings from 0.8 gal to 1.3 gal depending on condition — the difference between buying one gallon and two. The deck stain calculator lets you pick condition.

Always count the railing

Railings are the most-forgotten coverage item on every deck job. A typical 16×12 deck (192 ft²) with 30 lin ft of railing has roughly 120 ft² of railing surface when you count balusters, top and bottom rails, and the rim around the deck — that's another 60% on top of the deck floor. Forget the railing and you'll run out of stain mid-project.

Quick estimate: railing surface area ≈ railing perimeter × 4 (approximation that catches both faces of the rim plus both sides of the balusters and rails). The calculator builds this in.

Two coats is the default

Most stain manufacturers spec two coats on new or recoated decks. The first coat soaks into the wood and acts as a primer-sealer; the second is the durable color and UV coat. One coat works only on:

  • Light recoats over sound existing stain that's just worn
  • Solid-color stains designed for one-coat application (read the label — they exist but are rare)
  • Penetrating oils where you'd rather have a faded look on year 2

Skip the second coat and you'll restain in 2-3 years instead of 4-5.

Penetrating vs film-forming

Stain breaks into two technology categories that affect coverage and longevity:

  • Penetrating oil-based stains (Penofin, Sikkens Cetol) soak into the wood. Coverage runs higher on the bottle (300-400 ft²/gal) but the actual life is 2 years on horizontal decking, 3-4 on railings.
  • Film-forming acrylics (Behr Premium Solid, Cabot Solid Color) sit on the wood and form a paint-like layer. Coverage of 250 ft²/gal is typical; life on horizontal deck boards is 3-5 years before peeling starts.
  • Hybrid semi-transparents (Cabot Australian Timber Oil, Ready Seal) split the difference. Coverage and life land between the two extremes.

Common errors

Staining over a wet deck. Stain needs bone-dry wood — moisture meter under 15% on horizontal surfaces. Stain on damp wood traps moisture below the finish; the stain peels in patches within one season.

Skipping the cleaner-and-brightener. Old stain residue and weathered surface cells block new stain from bonding. A wood cleaner (Restore-A-Deck, oxalic acid brightener) on the day before staining nearly doubles the finish life.

Staining in direct sun. Stain dries before it penetrates on a 90°F sunny board. Result: lap marks, blotchy color, premature flake. Stain in shade or on overcast days when the wood surface is below 80°F.

Quick FAQ

How much stain for a 200 sq ft deck? About 1 gallon for smooth wood, 2 gallons for weathered, both with two coats. Add 1 more gallon if you have railings.

Can I use deck stain on a fence? Yes — the same products work on vertical wood, and coverage is typically 25% better on vertical (300 ft²/gal smooth) because there's less penetration.

How long between coats? Read the label, but most stains call for 4-12 hours between coats. Below 50°F or above 90°F, extend the cure window. The second coat goes on as soon as the first is dry to the touch but not before.

Estimate only. The deck stain calculator uses standard manufacturer coverage rates. Real coverage varies by product, wood species, and surface texture — verify with the spec sheet for the exact stain you're buying.