By Zencalcy Editorial TeamLast reviewed About us
Stain coverage depends on the wood: a dense new deck might take 250 square feet per gallon, while weathered cedar can drink twice that. Railing and stairs add area that is easy to forget — a railing run is roughly three times its linear length in square feet.
Gallons of stain for a deck, rails and stairs.
Area = L × W Units = ⌈Area × (1 + waste) ÷ coverage⌉ Cost = Units × price
One gallon covers 250 sq ft per gallon. Units are rounded up because suppliers sell whole gallons, and the waste allowance covers cuts, mistakes and future repairs.
| Symbol | Meaning |
|---|---|
| L, W | Room length and width (or wall length and height). |
| A | Area to cover, in square feet. |
| w | Waste allowance as a percentage. |
| N | Number of gallons to buy, rounded up. |
240 sq ft × 2 coats = 480 sq ft, plus 10% = 528 sq ft, so three gallons at 250 sq ft per gallon.
Continue with the Paint Calculator, Wallpaper Calculator, Tile Calculator, or the Flooring Calculator — or browse more home & garden projects and all construction calculators.
One gallon per 250 sq ft per coat on smooth wood; half that on rough or weathered boards.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026