I need to prorate a lease that starts tomorrow. The monthly amount is 1200. Please tell me this formula?

Thank you,
Rita

Why, since normally there is no allowed reason to break a lease. And if you allow someone out or find a new tenant. But even then rental notices are from pay period to pay period, so I can't think of any reason to prorate a lease.

But if done, amount divided by number of days in the month equals total due a day times days living in unit.