Home › Deck stain calculator
Deck Stain Calculator: How Many Gallons?
Estimate deck stain for the floor boards, railings and stairs. The calculator adjusts for the type of stain, the number of coats and how weathered the wood is, and finds the cheapest mix of 1 and 5 gallon cans.
How to estimate deck stain
- Floor: deck length × width.
- Railings: railing length × height × about 1.5, which covers both sides of the balusters, the top and bottom rails and the posts.
- Stairs: about 4 sq ft per step for a 36 in wide stair (tread, riser and stringer sides).
- Divide the total by the coverage on the can, then multiply by the number of coats. Weathered wood soaks up 25 to 50% more.
Worked example
A 16 × 12 ft deck has 192 sq ft of floor. Forty feet of 3 ft railing adds 180 sq ft, and four steps add 16 sq ft, for 388 sq ft. Two coats of semi-transparent stain at 200 sq ft per gallon need 3.9 gallons. Four 1 gallon cans ($160) are cheaper than a 5 gallon pail ($175), but if the wood is weathered you need about 4.9 gallons and the pail wins.
Coverage by stain type
| Type | Coverage per gallon | Lasts about |
|---|---|---|
| Clear sealer / toner | 200 to 300 sq ft | 1 to 2 years |
| Semi-transparent | 150 to 250 sq ft | 2 to 3 years |
| Solid color | 150 to 200 sq ft | 3 to 5 years |
Check the label: oil-based penetrating stains and water-based stains vary, and many brands tell you to apply only one coat on dense hardwoods.
Tips for a longer-lasting finish
- Clean the deck with a deck cleaner or brightener and let it dry for 48 hours before staining.
- Do the water test: sprinkle water on the boards. If it soaks in within a few minutes, the wood is ready for stain; if it beads, wait or strip the old finish.
- Apply wet-on-wet when a second coat is recommended, and back-brush to work stain into the grain. Do not let thick puddles dry on the surface; they peel.
- New pressure-treated lumber often needs to dry for a few weeks to months before it will absorb stain.
Planning a new deck? Start with the deck calculator.
Frequently asked questions
How much stain do I need for a 12x16 deck?
The 192 sq ft floor alone takes about 1 gallon per coat of semi-transparent stain. With 40 ft of railing and a short stair, two coats need about 4 gallons, or 5 if the wood is weathered.
How many square feet does a gallon of deck stain cover?
Usually 150 to 300 sq ft per gallon. Transparent stains and sealers go further; solid stains and rough or weathered wood use more.
Should I apply one or two coats of deck stain?
Many semi-transparent and solid stains recommend two thin coats applied wet-on-wet. Dense woods and some penetrating oils take only one coat, so follow the label.