That depends on how wide your board is.
A six inch wide board will need 25 x 25 x 2 (1250) linear feet to cover the area.
A three inch wide board will need 25 x 25 x 4 (2500) linear feet to cover the area.
25.
I have never seen linear used on a paint can, but if it is brush paint, you would have to assume a foot wide stripe so that would be 25 sq. ft. If it is a spray can, you would have to see how wide a pattern it has at the distance recommended on the can and figure from there.
Imagine a room 25 feet by 13 feet. That room has an area of 25 x 13 or 325 square feet.
25 feet 0 inches.
Imagine a room that measures 25 feet by 20 feet. The area of the floor in that room is 25 X 20 or 500 square feet.
Square feet is a unit of area and linear feet a unit of length. The two cannot be directly converted.
Total square feet: 625.0
600ft2
25
25' x 15' = 375 square feet.
14' x 25' = 350 square feet.
It is: 25 times 16.5 = 412.5 square feet