Energy density versus pressure?

[Sanev]

If i have Energy Density (U) -> U.Area= F but F.Area = pressure (p) but p must be U . I'm confused! In which cases we can say that energy density is pressure?

 

[A.T.]

If i have Energy Density (U) -> U.Area= F but F.Area = pressure (p) but p must be U . I'm confused! In which cases we can say that energy density is pressure?

http://hyperphysics.phy-astr.gsu.edu/hbase/press.html