Deck Stain Calculator

Enter your deck size, railings and stairs to see how many gallons of stain to buy.

How the calculation works

• Deck floor: length × width.
• Railings: about 6 sq ft per foot of railing, which covers both sides of the posts, rails and balusters on a standard 36" railing.
• Stairs: about 12 sq ft per step for a 4 foot wide stair, counting the tread, riser and stringers.

The total area times the number of coats, divided by the coverage per gallon, gives the gallons. Coverage depends on how thirsty the wood is, so check the can. Most list a range, such as 150 to 300 sq ft per gallon.

Worked example

A 16 × 12 foot deck (192 sq ft) with 40 feet of railing (240 sq ft) and 4 steps (48 sq ft) has 480 sq ft to stain. Two coats at 200 sq ft per gallon need 4.8 gallons, so buy five 1-gallon cans or one 5-gallon pail.

Tips

• Clean and dry first. Wash the deck with a deck cleaner, then let it dry for 24 to 48 hours. Stain won't soak into damp wood.
• Test absorption: sprinkle water on the boards. If it soaks in within a few minutes, the wood is ready for stain.
• Second coat timing: many penetrating stains go on "wet on wet", with the second coat about 20 minutes after the first. Read the label.

Frequently asked questions

How much does a gallon of deck stain cover?

Usually 150 to 300 square feet for one coat. Rough, weathered or new pressure-treated wood absorbs more, so expect the low end.

Do I need two coats of deck stain?

Most semi-transparent and solid stains recommend two coats. Some penetrating oil stains are made for one coat only, and a second coat can leave a sticky film. Follow the product label.