Deck stain calculator

How much deck stain do I need

Add up every surface you will stain, then divide by the square feet one gallon covers, coat by coat. The calculator does that for the floor, the railings and the stairs, and rounds up to a whole gallon.

Take a 16x12 ft deck, 36 in off the ground, so it gets a guard on its open sides. The floor is 192 sq ft. The railing adds 240 sq ft across 85 balusters, 8 posts and 39 ft of rail and cap. That is 432 sq ft. Two coats of Behr Premium Semi-Transparent on rough wood, the first at 250 sq ft per gallon and the second at 500, come to 2.6 gallons, so you buy 3. On smooth new wood at the top of the range it is 3.

Lower the same deck to 24 in and no guard is required, so the area falls to 192 sq ft and the order to 2 gallons. The height is how the calculator knows whether there is a railing to stain.

Coverage by stain type

Coverage moves the answer more than anything else, and the makers print it per coat. These are the figures on each product page, read Nov 6, 2026.

Old, dry wood drinks the first coat, so expect the low end there. Another brand will differ, so if your can is not on this list, use the rate printed on it.

Railings and stairs take more than you think

A deck floor is one flat rectangle. A railing is dozens of small parts, and every one has four faces.

Balusters

A 2x2 baluster is 1.5 in square, so at 36 in long its four faces come to 1.5 sq ft. Spaced at 5 in on center, the example deck takes 85 of them: 128 sq ft on balusters alone, before the posts, the rail and the cap.

Stairs

Stairs add treads, closed risers when the stair is over 30 in high, and the faces of the stringers. Add a 4 ft wide stair to the 36 in example and the stairs, with their railings, add 92 sq ft, which takes the total to 524 sq ft and the order to 4 gallons. Stringers are counted at their full 2x12 face, so the figure errs on the generous side.

Cost to stain a deck

The stain is gallons times the price of a gallon, or of a five-gallon pail when the count lands near five. We read Olympic Maximum Semi-Transparent at the Home Depot Hamilton Mill store on Nov 6, 2026: $47.98 a gallon and $229.00 for 5 gallons, before tax. One coat on the 16x12 ft example at 36 in is 1.7 gallons at 250 sq ft per gallon, so $95.96 for 2 gallons. The Behr lines use Home Depot listing prices and the Cabot lines use Lowe's and online retailer listing prices, all read from search listings rather than at a store, so treat them as estimates. We have no named, dated price for hiring the job out, so there is no installed number here: get written quotes.

When to stain new pressure-treated wood

The label decides, and makers differ: some say to wait until the wood dries out, which can take weeks to months. A common rule of thumb is the water drop test: sprinkle water on the boards. If it beads up, the wood is still wet from treatment. If it soaks in within a few minutes, it is ready. That is practice, not a standard, so read your can first.

Get the whole deck plan

This page sizes the stain. The deck designer sizes the deck: framing, guards, balusters and stairs, with the $49 plan carrying the full material list. For the boards alone, run the deck material calculator; for the railing parts, the deck railing calculator; for the stairs, the stair stringer calculator. For the cost of building the whole deck, see the deck cost guide.