That depends on the density of the ointment. You did not provide enough information to answer the question. It's like asking "How much room does 10 pounds of stuff take up?" Well... are we talking...
Gentamicin ointment is to be used externally for skin infections and such while Gentamicin ophthalmic ointment is for the eyes ONLY! Also, if it is an old prescription OR someone else's script, DO...
Heres a very basic ointment
8 oz lard by weight 2 oz (4 tbsp) beeswax
Melt wax in top of double boiler and add lard gradually. Stir till cool.
Can be varied by using a cooking oil (ie. olive,...