Deck and fence stain calculator
How many gallons of stain or sealer a deck or fence needs, from its size, the number of coats and the coverage on the can.
Coverage varies widely between products and with how weathered the wood is: use the figure on the can. Rough or old wood can take twice as much as smooth new boards.
How to use it
Choose deck or fence. For a deck, enter the length and width of the floor. For a fence, enter its length and height and whether you're staining one side or both. Then enter the number of coats and the coverage printed on the can, in square feet per gallon.
Coverage is the number to get right. It differs a lot between products (thin transparent stains spread further than thick solid ones) and between boards: new, smooth wood absorbs far less than old, rough or weathered wood. If the can gives a range, use the lower figure for old wood.
How it's calculated
- Deck area = length × width. Fence area = length × height × sides.
- Gallons = area × coats ÷ coverage.
- That's rounded up to whole quarts, and 3 quarts become a gallon, since a gallon usually costs about the same as three quarts.
At 200 sq ft per gallon, two coats:
| Project | Area | Stain |
|---|---|---|
| 10 × 12 ft deck | 120 sq ft | 1 gallon + 1 quart |
| 12 × 16 ft deck | 192 sq ft | 2 gallons |
| 16 × 20 ft deck | 320 sq ft | 3 gallons + 1 quart |
| 50 ft of 6 ft fence, both sides | 600 sq ft | 6 gallons |
| 100 ft of 6 ft fence, both sides | 1,200 sq ft | 12 gallons |
Tips
- Add the extras: railings, stairs and the sides of boards take stain too. A rough allowance is to add 10 to 20% for a deck with railings.
- Picket fences with gaps need a little less than a solid fence of the same size. The calculator treats the fence as solid, so it errs on the side of having enough.
- Test first on an offcut or a hidden spot. The color on new wood can look very different from the chip.
- Stain in the shade, not in direct midday sun, so it soaks in before it dries.