Update fails, lack of space, but have space

[Menel]

Settings.app indicates 1.6GB Available.

Application is 850MB, already installed, has an update available that will not run, error message says lack of space.

I don't understand

 

[FreakinEurekan]

If the app doesn't have irreplaceable user data, try deleting the app from the phone and re-installing it.

 

[dotme]

Space may be needed to un-compress file(s).

 

[Interstella5555]

Space may be needed to un-compress file(s).

This. It also depends how the app is updating, if it's doing the full 850GB file, then you have install app (850MB+) + Update (probably over 900) + unpacking = at least 2GB free needed to do everything. you'll get the space back, for to fully update it likely needs all that space.