Net Operating Income (NOI) is a measure of profitability most often used with income producing real estate businesses.
In the real estate world, net operating income is calculated by taking all revenues generated by a property (rent, parking, etc…) from all of the operating expenses needed to upkeep the property, which can include insurances, taxes, maintenance, utilities, and so on.
Net Operating Income is a before tax figure, so does not include principal and interest payments on loans, depreciation and amortization. If the NOI figure is negative, it is referred to as a net operating loss (NOL).