Deck Stain Calculator
Enter the deck top, and the rails and stairs if you are staining them, choose the coats and the coverage of one gallon, and get the gallons needed, rounded up once to whole cans of the size you buy.
Estimates for planning, not professional advice. Read the full notice.
Example: a deck top
2 1 gal cans
- Stain needed at the low end of the range, 250 square feet a gallon (the count that is bought, so it never falls short), in gallons 1.536 gallons
- Stain at the high end of the range, 350 square feet a gallon, for comparison, in gallons 1.097 gallons
- Gallon cans at the high end, for comparison 2 × 1 gal cans
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Deck stain | 1 gal can | 2 |
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Worked example: a deck top
Show the working
- Area of the top 16 ft × 12 ft = 192 ft²
- Gallons: the area times the coats, over the coverage of one gallon 192 ft² × 2 coats ÷ 250 ft²/gal[1] = 1.536 gallons
- Round up once, to whole cans 1.536 gallons = 2 × 1 gal cans
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Coverage of one gallon of deck stain, low end | 250 ft²/gal[1] | |
| Sherwin-Williams says one gallon of deck stain typically covers about 250 to 350 square feet, depending on the wood. | ||
| Coverage of one gallon of deck stain, high end | 350 ft²/gal[1] | |
| Sherwin-Williams says one gallon of deck stain typically covers about 250 to 350 square feet, depending on the wood. | ||
Feet and inches, like 12' 6"
Gallons for a deck top, by size and coverage
Gallons of stain for the top of a deck at two coats, by deck size and by the coverage of one gallon, with the gallon cans at the first coverage
| Deck top | Gallons at 250 square feet a gallon | Gallons at 300 square feet a gallon | Gallons at 350 square feet a gallon | Gallon cans at 250 |
|---|---|---|---|---|
| 10 ft by 10 ft | 0.8 gallons | 0.67 gallons | 0.57 gallons | 1 cans |
| 12 ft by 12 ft | 1.15 gallons | 0.96 gallons | 0.82 gallons | 2 cans |
| 12 ft by 16 ft | 1.54 gallons | 1.28 gallons | 1.1 gallons | 2 cans |
| 16 ft by 20 ft | 2.56 gallons | 2.13 gallons | 1.83 gallons | 3 cans |
| 20 ft by 20 ft | 3.2 gallons | 2.67 gallons | 2.29 gallons | 4 cans |
The first and last coverages are the two ends of the maker's range; the middle one is ours. The gallons are exact; the cans are rounded up once. Rails and stairs add to the total in the calculator above.
The maker's coverage range for deck stain
How many square feet one gallon of deck stain covers, as the maker prints it
| End of the range | Coverage of one gallon |
|---|---|
| Low end, Sherwin-Williams | 250 ft²/gal |
| High end, Sherwin-Williams | 350 ft²/gal |
Figures in the Coverage of one gallon column are per Sherwin-Williams' product page, checked Nov 12, 2026.
Product names are trademarks of their owners. HoneyDoMath is not affiliated with, sponsored by or endorsed by these makers. Figures come from each maker's published sheets and are shown for information only.
Source: [1]
The coverage depends on the wood; your own stain's label gives its own figure.
Questions
How much deck stain do I need?
Multiply the area by the coats and divide by the coverage of one gallon. The deck top in the example is 1.54 gallons at the low end of the maker's range, so the example buys whole cans. Your label gives the coverage for your own stain and wood.
Which coverage does the count use?
The maker prints a range, 250 to 350 square feet a gallon. The calculator starts at the low end, 250, so the count never falls short; the example shows the gallons and cans at 350 beside it. Choose 350 in the coverage select to count with the high end instead.
How many coats of deck stain are there?
That is your choice: the coats select takes one, two or three, and the gallons scale with it. The calculator does not pick a number; your stain's label says how many coats it is made for.
Why does the coverage change so much?
The maker's range depends on the wood, and rough or weathered boards take more. That is why the calculator asks for a coverage instead of assuming one: the low end, the high end and a figure between are the choices.
Sources (1)
-
How to Plan for Deck Staining (opens in new tab), The Sherwin-Williams Company, web page, no date shown.
Manufacturer data.
“Typically, one gallon covers about 250-350 square feet, depending on wood type.”
Per Sherwin-Williams' product page, checked Nov 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.
Sources
- [1] Sherwin-Williams, How to Plan for Deck Staining. Checked November 12, 2026. https://www.sherwin-williams.com/en-us/project-center/stain/how-to-plan-deck-staining