ConverterHub

Deck Stain Calculator

Buy just enough stain to finish the deck in one go.

How it is calculated

The tool divides the area to be stained by how far one gallon of the product spreads: gallons = ceil(area ÷ coverage). Area is in square feet and coverage is in square feet per gallon, as printed on the can. The result is rounded up to a whole gallon, and the litres are that whole number of gallons times 3.785. If you leave coverage empty, or enter zero or a negative number, the tool quietly uses 200 sq ft per gallon instead. There is no coats field, so the tool calculates a single coat; for two coats, enter twice the area. It also does not subtract gaps between boards or add the railings and stairs, so measure the total surface that you will actually coat.

Worked example

A deck and its steps add up to 420 sq ft, and the stain can says 150 sq ft per gallon on rough, thirsty wood. Divide: 420 ÷ 150 = 2.8 gallons. A partial gallon cannot be bought, so the tool rounds up to 3 gallons. In litres: 3 × 3.785 = 11.4 L. For a second coat, enter 840 sq ft: 840 ÷ 150 = 5.6, so you would buy 6 gallons (22.7 L) for both coats.

Try this example →

Common mistakes

  • Assuming the tool multiplies by coats. It does not, so a two-coat job needs double the area entered or the quantity will be half what you need.
  • Entering the coverage printed for smooth, sealed wood while staining rough, weathered boards that soak up much more, so the can runs out early.
  • Entering the area in square metres. The tool works in square feet and the area would come out about ten times too small.
  • Leaving coverage blank and not noticing that the tool then falls back to 200 sq ft per gallon, which may not match your product.
  • Measuring only the top of the deck and forgetting railings, balusters, stairs and the edges of boards.

About this calculator

Deck stain quantity is estimated by dividing the deck’s surface area by the product’s coverage rate — typically expressed in square feet per gallon — and rounding up to whole gallons: gallons needed = area ÷ coverage rate, for one coat. If you plan more than one coat, multiply the result by the number of coats. Coverage rate varies significantly by product type and wood condition: solid-color stains and new, smooth wood cover closer to 250-300 sq ft per gallon, while semi-transparent stains on rough-sawn or weathered, porous wood can drop below 150 sq ft per gallon because the wood soaks up far more product.

DIY homeowners and professional deck contractors use this calculation to buy the right amount before starting a refinishing job, since running short mid-project means an unplanned store run and a visible lap mark where old and new stain meet on a partially dried section, while over-buying wastes money on a product that doesn’t keep well once opened.

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