Deck Stain Calculator
With the deck stain calculator, you can easily estimate the volume of stain that you need to cover your deck.
Paint needed2.88 gallons10.9 litres, so buy 3 one-gallon cans
Per coat1.44 gallons
Net area to paint360 sq ft360 sq ft less 0 for openings
Total area painted720 sq ft2 coats
Deducted for openings0 sq ft0 doors at 20 sq ft, 0 windows at 15 sq ft
In 5-gallon buckets0.576usually cheaper per gallon above about 4 gallons
Primer, if bare1.44 gallonsone coat over the same area
The method
gallons = area × coats ÷ coverage per gallon
Two coats, and buy whole cans
A gallon covers about 350–400 square feet in one coat on a smooth primed wall. Rough render, bare drywall and dark-to-light changes all drink more, so check the tin — manufacturers state a figure and it is usually optimistic.
Deducting 20 square feet for a door and 15 for a window is the trade convention. It is deliberately conservative: if you plan to paint the trim as well, do not deduct at all.
Buying one extra can is nearly always the right call. Running out mid-wall means a visible lap line, and a second batch may not match exactly.