Stain coverage is smaller than paint
Deck stain soaks into wood instead of sitting on it, so one gallon covers about 250–300 sq ft per coat on new boards, and rough or old wood drinks even more. The calculator counts deck area × coats at 250 sq ft per gallon — a conservative number that keeps you from running out with half a railing left.
Do the verticals and the underside
Railing balusters add surprisingly fast (count each side), and staining the deck's underside and joists before decking is the pro move on new builds. Two light coats applied wet-on-wet beat one heavy coat — heavy coats stay tacky and attract dirt.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- American Wood Council — span tables, lumber design values and the Wood Frame Construction Manual.
- APA — The Engineered Wood Association — panel span ratings and sheathing installation guidance.
Figures, formulas and reference tables last verified: 19 September 2026.