The first step to calculating your personal net cash flow is calculating all of your sources of income, such as salary, wages, rental income, social security, investment income, bank interest, etc.
The next step is to calculate the income tax payable on your income based on the current year individual tax rates, being sure to exclude any tax free income.
Then, calculate all of your lifestyle expenses, such as mortgage repayments, rent, groceries, travel, etc.
Once you have these figures, you deduct your income tax and lifestyle expenses from your total income and whatever is left is your cash flow surplus. You can then direct this to your loans, investments, superannuation and retirement plan.