Hi! My name isXXXXX far as I know there is not set formula when dealing with non profit issues. But you do have to factor in operating cost, such as renting the theatre. Are you putting money into new costumes? Are you paying to have the stage redesIgned?
Usually, alot of the work is done on a voluntary basis as well as the actual performances.
But do figure up anything you have to spend, because you will want ticket prices to cover that and well as make money for your charity cause to increase your donation.
Good luck with the show!