Menu

Reviewed · Prices checked October 2026 · How we calculate

Deck Stain Calculator: How Much Stain Do I Need?

Enter the deck's size and the number of coats. You get the gallons of stain to buy; the second coat takes about half as much as the first.

Inputs

Units
Shape
ft
ft

    For railings and stairs, add them as more areas: length × height of each side you'll stain.

    Coats
    $

    Shopping list

    Updates as you type
    2gallons

    of semi-transparent deck stain for 192 sq ft, 2 coats (1.15 gal needed)

    Type your price per gallon for the cost—
    Show the math
    Area: 16 × 12 ft = 192 sq ftFirst coat: 192 ÷ 250 = 0.77 gal; second: 192 ÷ 500 = 0.38 gal → 2 gallons

    The price you type is used for this estimate only; it isn't saved.

    How it works

    The formula

    gallons = area ÷ 250 (first coat) + area ÷ 500 (second coat), rounded up

    Assumptions

    • Coverage: BEHR PREMIUM Semi-Transparent lists 250 to 300 sq ft per gallon for the first coat and 500 to 600 for the second; we use the low ends. Solid and transparent stains differ, and rough or weathered wood drinks more: check your can.
    • The area is the walking surface; add railings, stairs and skirting as more areas.

    Worked example

    A 16 × 12 ft deck, 2 coats

    1. 192 ÷ 250 + 192 ÷ 500 = 1.15 → 2 gallons

    Gallons by deck size, 2 coats

    Gallons of semi-transparent stain for 2 coats by deck size, floor only
    DeckGallons neededBuy
    10 × 10 ft0.601
    12 × 16 ft1.152
    16 × 20 ft1.922
    20 × 24 ft2.883

    Questions people ask

    How much deck stain do I need?

    For two coats of semi-transparent stain, about 1 gallon per 170 sq ft: the first coat covers about 250 sq ft per gallon and the second about 500. A 16 × 12 ft deck takes 2 gallons.

    Do I need two coats?

    Many semi-transparent stains call for two thin coats, the second applied before the first dries. Read your can; some products are one-coat.

    When can I stain a new deck?

    When the wood takes water: sprinkle some on, and if it soaks in, it's ready. Pressure-treated lumber often needs a few weeks to a few months.