Climp gradient

[C340]

Dear all,

I have recently flown into Thessaloniki, Greece RWY 10 an ILS DME procedure. Now my quastion is : for DA there are two different altitudes with significant difference of 400+ ft. This is due to a different climb gradient set, one with 4.0% and the other with 2.5% min.

How can you calculate what your climb gradient is in % and in ft/ min???

Thanks