Deck stain calculator

Stain by type and by how thirsty the boards are, with the coat limit the tin actually allows.

Stain type
Units
Wood condition

Optional. In square feet, if you already have it.

Transparent and semi-transparent are one coat only.

Add the railing

Total run, both sides of a stair included.

Bottom rail to top rail, not deck to handrail.

Count them, or divide the run by your spacing.

Across one face. Rails are counted at the same width.

Add a price

Optional. Leave blank and the estimate shows quantities only.

Enter your deck size to see how much stain to buy.

    Two variables, not one

    Almost every deck stain calculator asks for an area and divides by a single coverage number. The manufacturers publish three coverage ranges, not one figure — and every data sheet adds that weathered wood needs more than new. Between them those two facts move the answer by more than double.

    transparent 200–400 ft²/gal max 1 coat semi-transparent 150–350 ft²/gal 1 coat solid colour 200–400 ft²/gal max 2 coats new smooth wood → the top of the range weathered or rough → the bottom of the range gallons = ceil(area × coats ÷ coverage)

    The coat limit is not advice

    Transparent oil stain says do not apply more than one coat. It is a penetrating finish: the wood absorbs what it can and a second coat has nowhere to go, so it sits on the surface and stays tacky for weeks. This calculator will not quote you a second coat of it. Solid colour stain is a film former and allows two.

    Common mistakes

    • Measuring the deck surface only. Railings and spindles can add half as much area again.
    • Using one coverage number for every product. The three types genuinely differ.
    • Treating weathered boards as new. The same tin covers roughly half as much ground.
    • Buying a second tin later. Stain is tinted per batch and a later tin can shade differently.

    The rest of the deck

    If you are still building it, the deck board calculator counts the boards and the deck footing calculator sizes the concrete underneath.

    Stain needed for a 200 ft² deck, one coat

    Stain typePublished coverageWeathered woodNew woodMax coats
    Transparent200–400 ft²/gal1 gal1 gal1
    Semi-transparent150–350 ft²/gal2 gal1 gal1
    Solid colour200–400 ft²/gal1 gal1 gal2

    Deck surface only. Add railings, stairs and fascia separately — they are not in this 200 ft².

    The rest of the deck

    Stain is the last job on a deck and rarely the only one. The deck board calculator works out the boards and the rows they land in, the deck footing calculator sizes the tubes and the concrete under them, and the board foot calculator prices framing lumber the way a yard quotes it. If the deck is an awkward shape, take the area from the square footage calculator and bring it back here.

    Plan view of a 16 by 12 foot deck, the area a stain quantity is figured on.
    Drawn to scale.

    Common questions

    How much stain do I need for a deck?

    For a 200 square foot deck in semi-transparent stain, one to two gallons — and which of those it is depends entirely on the wood. New smooth boards take a gallon; weathered boards can take two, because old wood is far more porous and drinks the first coat. That is not a hedge: it is the note printed on the manufacturer data sheet for every one of these products.

    Does the type of stain change how much I need?

    Substantially. Semi-transparent is published at 150 to 350 square feet per gallon; transparent and solid both at 200 to 400. Most calculators quote a single figure and are therefore wrong for two of the three products. Pick your type above and the number changes with it.

    How many coats of deck stain should I apply?

    Usually one, and for some products one is the maximum. Transparent oil stain says plainly: do not apply more than one coat. Semi-transparent needs only one. Only solid colour stain allows two. This calculator refuses to compute more coats than the product permits, because a second coat of a penetrating stain has nowhere to go and stays tacky on the surface.

    Why does weathered wood need more stain?

    Because it is more porous. A new board has a relatively closed surface and the stain sits in the top layer. Weathering opens the grain, and the first coat is partly absorbed rather than being available to cover. The published coverage ranges exist to capture exactly this, and the low end of each is the weathered case.

    Do I need to include the railings?

    Yes, and on a deck with a lot of balustrade they can add half as much area again. Spindles have four faces each and almost no footprint, so they punish an area-only estimate badly. Measure the railing, stairs and fascia and enter the total in the field above — the deck surface alone will leave you short.

    Is this figure the same for every brand?

    No. These are the published rates for one manufacturer’s three product lines, cited below with their data sheets. Another brand will be in the same territory but not identical, and the coverage printed on the tin you actually buy always wins over any calculator, including this one.

    Should I buy to the high or low end of the range?

    Low, which is what this does when you say the wood is weathered. Coverage is quoted in square feet per gallon, so the smaller number is the one that needs more product. Running out of stain halfway across a deck leaves a lap mark you cannot sand out without stripping the whole thing.

    Can I use this for a fence or for siding?

    Yes, and the coverage figures are the same — they belong to the stain, not to the deck. What changes is how you work out the area. A fence is stained on both sides, so a 100 foot fence 6 feet high is 1,200 square feet rather than 600, and picket edges drink far more than their flat faces suggest. Siding is a single face, but the laps and any texture take more per square foot than a smooth board. Work out the area, enter it as the deck area, and the published coverage per gallon does the rest.

    Why is there no separate fence stain calculator?

    Because it would be this page with a different heading, and a second page saying the same thing helps nobody. Stain coverage is a property of the product: a semi-transparent stain covers the same square footage per gallon whether that footage is horizontal decking, vertical fence boards or lap siding. What genuinely differs is the surface — how rough it is, how thirsty it is, and how many faces you are coating — and those are things you measure rather than things a different calculator would know.

    Sources

    Default waste allowance
    0%

    Coverage is a published range with no typical value, so none is stored: a midpoint would be a number the manufacturer never printed. Every one of these three data sheets carries the same note — new wood normally requires less product than old, weathered wood, because older wood is more porous — so the top of each range is smooth new timber and the bottom is rough or weathered timber. That is the manufacturer's own statement, not an interpolation. Maximum coat counts are published per product and differ: transparent is one coat only, semi-transparent needs only one, solid allows two. A calculator that offers three coats of transparent stain is offering something the tin forbids.

    Unit conversions are exact by definition and need no source.

    How we choose and cite these figures

    By Team MaterialMath. Published . Last checked . How these figures are sourced and checked.