No. 4 quarts more likely....and then maybe not enough. Figure 300-400 square feet per gallon.....average. Some super thick stuff is even less.

Really! a 6ft x 6ft deck is large? You may just get it done if you spread it out. And I thought my deck was small at 20' x 40' , But that only took 2 gallons of paint

It should. You get about 100 sq. ft. from a quart. You have a little less than 36 sq. ft.

One quart will give you plenty. You'll have enough for 2 coats and then some left over to throw out in 2 years. They should make it a law that paint be sold in pint cans to avoid waste in our landfills. Same for 1/2 gallons. Better yet, bring your own container and purchase what you need or the seller furnishes a container marked in segments of pints. Great marketing concept!