Deck Stain Calculator

Enter your deck dimensions, the number of coats, and your stain's coverage to estimate the gallons needed. Add extra for railings, stairs, and the gaps between boards, which all drink up more stain than flat math suggests.

How it works

Gallons = deck area × coats ÷ coverage. Deck stains cover roughly 150–300 square feet per gallon depending on the wood's porosity and texture — rough or weathered boards absorb far more than smooth, sealed ones.

Worked example

For a 16 ft × 12 ft deck (192 sq ft) plus railings, figure the deck surface at 192 sq ft. If a gallon of stain covers ~250 sq ft on smooth wood, that's about 1 gallon for one coat — but rough or older boards drink more, dropping coverage to ~150 sq ft/gal, which pushes you toward 1.5 gallons. Railings and stairs add surface area, so round up.

What changes your estimate

• Wood condition. New smooth boards cover near the high end of the range; weathered, rough, or thirsty wood needs far more per square foot.
• Number of coats. Two coats roughly double the stain needed — check the product's recommendation.
• Railings and stairs. Vertical surfaces and balusters add a surprising amount of area beyond the deck floor.
• Stain type. Transparent and semi-transparent stains spread further than solid-color stains, which are closer to paint in coverage.

Frequently asked questions