Deck stain calculator: how much deck stain do I need?
1 gallon
0.55 gallons exact · 192 sq ft at 350 sq ft per gallon, 1 coat · for a 16 × 12 ft deck at 350 sq ft per gallon
Run your own numbers
Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
1 gallon
0.55 gallons exact · 192 sq ft at 350 sq ft per gallon, 1 coat
Source: BEHR Premium Semi-Transparent Waterproofing Stain & Sealer No. 4600, Technical Data Sheet (Behr Process Corporation), read October 17, 2026. Data sheet (PDF)
A 12 by 16 ft deck, 192 square feet, takes 1 gallon of a semi-transparent oil stain such as Behr No. 4600, whose data sheet gives 350 to 400 square feet per gallon in one coat: 0.55 gallons at 350.
A worked example
A 22 by 14.5 ft deck with 46 square feet of railings, two coats of a stain whose label says 250 square feet per gallon needs 3 gallons. The deck is 319 square feet, 365 with the railings; two coats make 730, and 730 ÷ 250 is 2.92 gallons, so 3.
How many gallons of stain for a 12x12 deck?
One. A 12 by 12 ft deck is 144 square feet, which one coat of Behr No. 4600 covers with 0.41 gallons at its 350 square feet per gallon. A 20 by 20 ft deck, 400 square feet, takes 1.14 gallons at 350, so 2 gallons, or exactly 1 at the 400 end of the range. Railings and steps add their own square feet: enter them above.
How much does a gallon of deck stain cover?
Whatever its data sheet says, because it changes from product to product. Behr No. 4600, a semi-transparent oil stain, gives 350 to 400 square feet per gallon in one coat, depending on how it goes on and how porous the wood is, and sprayed stain covers less than that. Read the coverage on your own can and type it in: the calculator divides your square feet by it.
What else it is called
A deck stain calculator is also searched as a stain calculator for deck, deck stain coverage or “how many gallons of stain for a 12x12 deck”. Semi-transparent, solid and clear sealers each print their own coverage, and the same brand name can cover differently as an oil and as a water-based formula: use the number on your can.
Gallons by deck size
| Deck | Square feet | Gallons at 350 sq ft/gal | Gallons at 400 sq ft/gal | Gallons to buy |
|---|---|---|---|---|
| 10 × 10 ft | 100 | 0.29 | 0.25 | 1 |
| 10 × 12 ft | 120 | 0.34 | 0.30 | 1 |
| 12 × 12 ft | 144 | 0.41 | 0.36 | 1 |
| 12 × 16 ft | 192 | 0.55 | 0.48 | 1 |
| 16 × 16 ft | 256 | 0.73 | 0.64 | 1 |
| 16 × 20 ft | 320 | 0.91 | 0.80 | 1 |
| 20 × 20 ft | 400 | 1.14 | 1.00 | 2 |
One coat of Behr No. 4600 semi-transparent oil stain, 350 to 400 sq ft per gallon by its data sheet; gallons to buy at 350. The deck floor only: add railings, steps and skirting as square feet in the calculator.
Where the numbers come from
- Starting coverage: the Technical Data Sheet of BEHR Premium Semi-Transparent Waterproofing Stain & Sealer No. 4600, an oil-based (alkyd) penetrating stain for decks, fences and siding: «Coverage: 350-400 sq ft/gal, depending on application method and substrate porosity. Does not include the loss of material from spraying.» and «One coat application.» The calculator starts at 350, the end that does not leave you short. Read October 17, 2026, and again October 18, 2026. Data sheet (PDF)
- Coverage is per product, so the calculator takes the figure printed on your can; the rest is arithmetic: square feet × coats ÷ square feet per gallon, rounded up to whole gallons.
Rough or weathered boards soak up more stain than new smooth ones, which is why the data sheet gives a range: a thirsty deck sits at the low end. Spraying loses material that the coverage figure does not count.
By Javier Miralles · Last updated . How this site is made.
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