How many cubic feet are in a army duffle bag?

Answer 1

Short answer: About 2.92 cubic feet

(You'd more commonly refer to it as an 80 liter bag)

Long answer...

Most are 36" long and 21" when spread out flat. We need to turn that into a three dimensional object. The base of these duffel bags is square but when filled the bag forms a sausage shape, so we're going to use a cylinder for our math. Since this is a flattened cylinder, that 21" is actually half the circumference of 42"

Radius = Circumference / (2 x pi)

Radius = 42" / (2 x pi)

Radius = 6.68"

Volume of cylinder = height x pi x radius^2

Volume = 36" x pi x 6.68^2

Volume = 5053 in^3

1 ft^3 = 12" x 12" x 12" = 1728 in^3

5053 in^3 / 1728 in^3/ft^3 = 2.92 ft^3