Deck Stain Calculator
Gallons of stain, railings included — coverage done right. Free, instant, and private — everything runs on your device.
0 if no railings
Deck stain runs $30–$55/gal
Your deck stain estimate
- Deck surface
- 192 sq ft
- Railings
- 168 sq ft
- Total (2 coats)
- 720 sq ft
- Exact usage
- 2.88 gal
- Estimated cost
- $126
Stain covers far less than paint — and old, dry, or rough boards drink it up, so lower the coverage if your deck is weathered. The first coat on bare wood always soaks in the most.
The reason people run out of deck stain halfway through the railings is simple: stain doesn't cover like paint. A gallon that would roll 350 square feet of drywall might only reach 150–250 square feet of decking — less on old, sun-baked, or freshly sanded boards that drink the first coat. This calculator uses the coverage rate for your stain type, adds the surprisingly large surface area of railings and balusters, and tells you how many gallons to actually buy.
Pick your stain type (clear toner down to solid), enter the deck footprint and how much railing you have, and set your coats. You'll get gallons to buy, the exact usage behind it, and a cost — so you finish the whole deck on one dry weekend instead of two.
How it works
No black box — this is the exact math the calculator runs.
- Deck surface = length × width, in square feet.
- Railings add about 3 sq ft of stainable surface per linear foot (two faces plus balusters).
- Coverage depends on stain type: clear ≈ 300, semi-transparent ≈ 250, semi-solid ≈ 200, solid ≈ 175 sq ft per gallon.
- Exact gallons = (total surface × coats) ÷ coverage.
- Gallons to buy rounds up to whole cans; cost = cans × your price per gallon.
Last reviewed July 24, 2026 · Fences & Outdoor Structures
Frequently asked questions
How much stain do I need for a 16x12 deck?
The deck floor is 192 sq ft. With a semi-transparent stain (about 250 sq ft/gal) and two coats, that's roughly 1.5 gallons for the boards alone — buy 2. Add railings and you're solidly into 2–3 gallons, which is exactly why railings belong in the estimate.
Why does deck stain cover less than paint?
Stain soaks into the wood rather than sitting on top, and horizontal deck boards weather far more than walls, so they absorb more. Older or rough-sawn boards can drop coverage below 150 sq ft per gallon — lower the coverage number if your deck is weathered.
Do I need one coat or two of deck stain?
Most semi-transparent and solid stains are designed for two coats, applied wet-on-wet or within the window on the label. Penetrating oil stains are often one heavy coat wiped back. Follow the can — over-applying film-forming stain causes peeling.
Should I stain the railings and stairs separately?
Estimate them, yes — railings, balusters, and stair stringers add a lot of surface for their footprint. This calculator lets you enter railing length so those gallons aren't a surprise at the store.