How this calculator works
Stain is spread over the surface area, and how far a gallon goes depends on the wood and the product: roughly 150 ft² on rough or new wood up to 300 ft² on smooth boards. We add up the deck and the other surfaces, multiply by the number of coats, and divide by the coverage.
Worked example: a 12 × 16 ft deck (192 ft²) with one coat at 200 ft² per gallon needs 0.96 gallons, so buy one gallon. Two coats would need about 1.9 gallons.
Tips before you buy
- Clean the deck first with a deck cleaner and let it dry for a couple of days. Stain applied over dirt or mildew will not last.
- Do not stain in direct sun or when rain is forecast for 24 hours. Cooler, overcast days give a more even result.
- Most penetrating stains want one thin coat. A second coat on top of a coat that has not absorbed can leave a sticky film.
- Stain the railings and spindles separately, as they take longer than the flat deck, and the area is larger than it looks.
Tools & materials for this project
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Frequently asked questions
How much stain do I need for a 12x16 deck?
About 1 gallon for one coat at 200 ft² per gallon (192 ft² of deck), or 2 gallons for two coats or for rough wood.
How many coats of deck stain do I need?
One for most penetrating stains. Two can be needed for opaque stains or very dry wood, as the label says.
Do I need to stain the railings?
If you want them to match, yes. Add their surface area to the calculator: roughly 3 to 4 ft² for each foot of a standard railing with balusters.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.