Deck paint and stain calculator
Enter the deck’s length and width, and the railing and steps if you are coating them too. Pick the product: deck paint and solid stains film over the wood; semi-transparent stains soak in, and weathered boards soak in a lot.
Enter your measurements
More options: Rail H · Steps · Stair W …
- Deck paint or stain needed
- 1.44 gal (5.45 L)
- Cans of the size you chose
- 2 cans · 1-gallon
- Surface to coat (one coat)
- 144 sq ft
- Paint per coat
- 0.72 gal
- Coverage used
- 200 sq ft/gal
Floor: 12 ft × 12 ft = 144 sq ft
144 sq ft × 2 coats ÷ 200 sq ft/gal = 1.44 gal → 1 gallon + 2 quarts
- Using a planning coverage for this product. Weathered, rough and soft woods soak up more; your can’s figure is better.
- Board edges and gaps take a little extra; the deck floor is counted as flat.
- Deck paints and solid stains form a film that can peel on horizontal boards. Clean and dry the wood thoroughly and follow the label’s recoat window.
- Old house? If it was built before 1978, read lead paint safety before you sand or scrape: EPA advises assuming old paint contains lead until it is tested.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How much paint for a 12x12 deck | 1.44 gal: buy 1 gallon + 2 quarts |
| How much paint for a 10x10 deck | 1 gal: buy 1 gallon |
| How much paint for a 12x16 deck | 1.92 gal: buy 2 gallons |
Deck coating by product (same deck and coats)
| Product | Deck paint or stain needed | Buy (gallons and quarts) |
|---|---|---|
| solid stain or deck paint | 1.44 gal | 1 gallon + 2 quarts |
| semi-transparent stain | 1.15 gal | 1 gallon + 1 quart |
| stain on weathered wood | 1.92 gal | 2 gallons |
The deck floor is length × width. Railings and steps are optional; under More options you can set the railing height and stair width. New to this? Paint words explained.
How the deck calculator works
floor = length × width railing ≈ balusters (4 faces × 1½ in × height, every 5 in) + 2 rails all round steps = steps × width × (11¼ in tread + 7¼ in riser) product = total × coats ÷ coverage
Where the coverage figures come from
Deck coatings spread far less than wall paint, because wood is porous and deck boards are rough. Sherwin-Williams’ WoodScapes Solid Color Stain lists 200–400 sq ft per gallon; its Semi-Transparent stain lists 100–350, depending on porosity and texture, and notes that weathered wood takes more product than new. The calculator plans solid stain and deck paint at 200, semi-transparent at 250 on newer wood and 150 on weathered or rough boards. Your label beats all three.
Worked examples
- How much paint for a 10x10 deck: exactly a gallon for two coats of solid stain.
- How much paint for a 12x12 deck: the classic platform deck, with and without the railing.
- How much paint for a 12x16 deck: two gallons, and what weathered boards do to it.
Staining rather than painting a new deck? The sister site’s wood stain calculator (opens in a new tab) covers clear finishes and furniture as well as decks.
Tips
- Clean the deck and let it dry for a couple of days before coating; stain applied over damp wood blotches and paint peels.
- Coat two or three boards at a time along their full length, so laps don’t dry in the middle of a board.
- Don’t over-apply penetrating stain: what doesn’t soak in stays tacky. Back-brush the excess.
- Check the label’s temperature and rain window. Most need a dry day or two and mild temperatures.
What you’ll need
- Deck stain pad and poleBudget price
Lays stain or deck paint down evenly across boards and works it into the gaps faster than a brush.
See options on Amazon (opens in a new tab) - Deck stain brushBudget price
A wide stain brush works stain into rough boards, end grain and railings where a pad can’t reach.
See options on Amazon (opens in a new tab) - Electric pressure washerMid-range price
Cleans siding, decks and fences before painting. Let wood dry thoroughly before you coat it.
See options on Amazon (opens in a new tab) - 5-gallon bucket and roller gridBudget price
Once a job needs more than two gallons, boxing the paint in a bucket keeps the color consistent and a grid replaces the tray.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much deck stain do I need for a 12x12 deck?
About 1.44 gallons of solid stain or deck paint for two coats on the floor, at 200 sq ft per gallon. See how much paint for a 12x12 deck.
Why does a deck take so much more paint than a wall?
Wood is porous, deck boards are rough, and weathered wood soaks in more. Deck stains list 100–400 sq ft per gallon against 350–400 for wall paint.
How do I estimate railings?
Enter the railing length; the calculator counts 1½ in balusters every 5 in on four faces plus two rails. That is about 5.3 sq ft per foot of 36 in railing, more than the floor area of a 1 ft strip of a 5 ft wide deck.
One coat or two of deck stain?
Semi-transparent stains are often one coat, or two thin coats wet on wet; solid stains and deck paints two. Follow the label.
Related guides
Sources
- Sherwin-Williams, WoodScapes Exterior Acrylic Solid Color Stain (A15-50 series), product data sheet (opens in a new tab) — Coverage 200–400 sq ft per gallon at 4–8 mils wet; two coats.
- Sherwin-Williams, WoodScapes Exterior Polyurethane Semi-Transparent Stain (A15T00005), product data sheet (opens in a new tab) — Coverage 100–350 sq ft per gallon depending on porosity and texture; weathered wood takes more than new.