What determines a Chapter 13 bankruptcy monthly payment?

In Chapter 13 bankruptcy, you create a repayment plan in which you repay your debts (in full or in part depending on the type of debt and other factors) over an extended period of time -- three or five years.

How much that monthly payment will be depends on several factors. 

Some debts must be paid in full. You must pay some debts in full over the life of your plan. These include priority debts (like child support and most tax debts), arrearages on secured loans (like mortgage arrears), and administrative expenses incurred in the bankruptcy, among others.

Unsecured debts. You must pay your unsecured creditors at least what they would have received had you filed for Chapter 7 bankruptcy. 

Disposable income. You must devote all of your disposable income (this is your income minus certain allowable deductions for living expenses) to your plan. 

To learn more about Chapter 13 repayment plans, see The Chapter 13 Bankruptcy Repayment Plan.