Deck Stain Calculator

Why This One Is Different

Deck stain coverage isn't one number because a deck isn't one surface: horizontal, sun-facing boards take the brunt of UV exposure and wear fastest, while weathered, gray, or previously-stained wood soaks up far more stain than fresh lumber. The first-coat range this calculator uses is roughly 150-300 sq ft per gallon (the low end for old, thirsty wood and the high end for new, tight-grained boards), and it defaults to one coat, what most re-stain jobs need. A second coat, by trade convention, typically covers more area than the first since the wood's pores are already partly filled; that's a practitioner rule of thumb, not a manufacturer spec, labeled as such rather than presented as fact.

Where the Numbers Come From

• First-coat deck stain coverage runs roughly 150-300 sq ft per gallon (a manufacturer PDS class range), with dense, new wood at the high end and weathered, porous wood at the low end. Source: deck-stain PDS class (coverage.ts engine convention)
• A second coat covers meaningfully more area per gallon than the first because the wood's pores are already partly filled: this is a trade convention, not a manufacturer-published multiplier, and is labeled as such rather than given a false precise number. Source: trade convention, labeled as such (not codified in a manufacturer PDS)
• Horizontal, sun-facing deck surfaces take the most UV exposure of any exterior wood surface and wear through a finish fastest, while vertical rail and skirt boards on the same deck can go noticeably longer between re-coats. Source: trade convention, labeled as such
• A mid-size 320 sq ft deck can need one gallon fewer just because the wood is in better shape: worked example, at one coat and the low end of the band (150 sf/gal) it needs 320÷150 = 2.13, rounding up to 3 gallons; at the high end (300 sf/gal) it needs 2 gallons. Source: worked example, coverage.ts formula