Construction & DIY
Deck Stain Calculator
Free deck stain calculator to estimate how many gallons of stain or sealer you need. Factors in deck floor area, railings, spindles/balusters, stairs, and 1 or 2 coats.
Calculates surface area for top rails, posts, and spindles/balusters
Typical quality deck stain: $40 - $60 per gallon
Stain Requirements
Stain Gallons Needed 0 gallons
Deck Floor Area 0 sq ft
Railings & Balusters Area 0 sq ft
Stairs & Risers Area 0 sq ft
Total Single-Coat Surface Area 0 sq ft
Estimated Material Cost $0
Coverage Note: The first coat on bare or aged wood absorbs roughly 60% of the total stain, while the second coat requires ~40%. If purchasing 5-gallon pails, consider buying one 5-gallon pail for larger projects over 700 sq ft.
How many gallons of stain for this deck?
Stain coverage on rough, weathered wood can be half of the can’s “smooth wood” number. Measure decking square footage, add railings and balusters (they eat stain), then multiply by coats. Two thin coats usually beat one heavy coat that peels.
What people under-buy
- Vertical pickets and the back side of rails
- Stairs (treads + risers)
- A second coat if the first soaked in on old cedar
Frequently Asked Questions
How many gallons of stain do I need for a 12x20 deck?
A 12×20 deck floor is 240 square feet. If you also have 32 linear feet of railing (~80 sq ft) and 4 steps (~24 sq ft), your total surface area is roughly 344 sq ft. For **2 coats on standard wood** (approx. 300 sq ft coverage per gallon per coat), you need **3 gallons of deck stain**.
How much square footage does 1 gallon of deck stain cover?
One gallon of quality deck stain typically covers **250 to 350 square feet** on smooth or previously maintained wood. On rough-sawn, heavily weathered, or porous unsealed wood, coverage drops to **175 to 225 square feet per gallon** as the wood absorbs significantly more liquid.
Do I need 1 or 2 coats of deck stain?
Most stain manufacturers (Cabot, Ready Seal, Behr, Olympic) recommend **2 coats** for maximum UV protection and water repellency on bare or freshly stripped wood. If you are doing an annual refresh with the exact same semi-transparent product, a single coat is usually sufficient.
How do I calculate railing and baluster surface area?
A good rule of thumb is to multiply the linear feet of railing by **2.5**. This accounts for the top handrail, bottom rail, posts, and all four sides of vertical 2×2 spindles (balusters).
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About these results: Figures are for planning only. Confirm anything you will buy, bill, or submit (materials, payroll, medical screening) against the label, a quote, or a professional.