Calculating NOI question:

[Noel Pingatore]

Hello - I'm having trouble understanding why we don't include the mortgage payment in the monthly expenses when we calculate the NOI. This is the formula as I understand it. NOI = annual rental income - annual expenses( excluding mortgage payment) Is this correct?

Every time I do this calculation I get a large NOI, or so it seems to me. So I think I must be missing something.

Any clarifications or insights would be greatly appreciated. 

Thank you