Deck Stain Calculator

Find out how many gallons of stain or sealer you need for your deck — floor plus railings — including coats, plus an estimate of the cost.

How to measure an area — length times width Length Width
Measure the deck floor — length × width. Add the railings option (or measure them) if you're staining those too.

How much deck stain do I need?

Deck stain is estimated just like paint — from the surface area, the number of coats, and how far a gallon goes:

Gallons = surface area × coats ÷ coverage per gallon, rounded up

The deck floor area is length × width. Railings, balusters, and stairs add a surprising amount of surface, so the railings option bumps the area by about 40%. We multiply by your coats, divide by the coverage (around 250 sq ft per gallon for semi-transparent stain on smooth wood), and round up to whole gallons.

Coverage by stain type and wood

Coverage is per gallon, for a single coat. Old, rough, or bare wood is thirsty and covers far less — lower the value to match your boards.

FinishCoverage per gallon (1 coat)
Clear sealer / toner250–400 sq ft
Semi-transparent stain150–300 sq ft
Solid-color stain200–300 sq ft
Old / rough / bare woodUse the low end

Tips for a lasting finish

  • Clean and brighten first. Strip old finish, wash, and let the wood dry for 24–48 hours before staining.
  • Go thin, not thick. Penetrating stains should soak in — wipe back any puddles. Two thin coats beat one heavy one.
  • One coat for many stains. Some semi-transparent and toner products are designed for a single coat; set coats to 1 if so.
  • Mind the weather. Stain at 50–90°F, out of direct sun, with no rain expected for 24–48 hours.

Frequently asked questions

How much stain for a 16×12 ft deck?
That's 192 sq ft of floor. At two coats and 250 sq ft per gallon, about 2 gallons — roughly 3 if you add railings and stairs.
One coat or two?
One to two thin coats for semi-transparent and penetrating stains; two for solid-color. Over-applying causes peeling, so follow the can.
Why does bare wood need more stain?
New, old, or rough wood soaks up the first coat, dropping coverage to as little as 150 sq ft per gallon. Lower the coverage value for thirsty decks.
Do railings really add that much?
Yes — balusters and stairs have a lot of surface and can add 20–50% over the floor. Use the railings option or measure them separately.

How we calculate this

  • Deck (and railing) area drives the estimate
  • Stain covers roughly 200–300 sq ft per gallon per coat (less on rough or thirsty wood)
  • Coats are multiplied in and gallons rounded up

Sources:Stain and sealer manufacturer coverage data. Last reviewed:June 2026. See our methodology for how we build every estimate.

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