The cap rate formula is simple. The formula is the following:
Cap Rate = Net Operating Income (NOI) / Transaction Price
According to textbook definitions (Greer and Farrell, 1992), the NOI used for the estimation of the cap rate, or the overall capitalization rate, is the projected net operating income of the property during the first year following its acquisition. Thus, taking into account the different time periods that the components of the cap rate formula refer to, the correct mathematical expression for this formula is :
CRt = NOIt+1 / TPt
Where:
CR= Cap Rate
TP= Transaction Price
t = year t, during which the transaction occurs
t+1= year t+1
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The cap rate actually represents the income return to the investor that is acquiring a property. For example, the cap rate, of a transaction involving a property expected to produce an NOI of $100,000 in the first year of its holding period and is sold for $1 million, is:
Cap Rate = 100,000/1,000,000 = 0.10 = 10%
The estimated cap rate represents and the income return in the firs year of the holding period and that is why it is often referred to as initial yield.
Data Issues in Applying the Cap Rate Formula
Several vendors are providing cap rate data by market and property type as well as by individual transaction. The reported market cap rates may have not been estimated using the exact cap rate formula provided above, especially, if the cap rate has not been provided by the parties directly involved in the transaction (buyer or seller). It is more common to announce publicly the price at which a transaction occurred rather than the cap rate of the transaction. In such a case data vendors may find information about the current NOI of the property and estimate the transaction cap rate using that information and the publicly announced sales price.
Notice that projections of next year NOI can be quite complicated for multi-tenant commercial properties with many tenants. First of all coming up with projections of rental income requires looking at the leases of each tenant, figuring out whether there are annual escalation clauses, what percentage increase is applied to each lease and what particular date of the year. There may be also expiring leases in which case it is necessary to make some assumptions as to whether they will be renewed and, if not, how long the space will remain vacant. In addition, operating expenses will depend on how much space is occupied. For this reason, in most cases in applying the cap rate formula to current market transactions for deriving market capitalization rates, it is more likely to have data on the current NOI of the property at the time of the transaction rather than projections for next year. In many cases, even the former piece of information is not known and some data vendors may use in the cap rate formula an estimated NOI based on market rents, which is then applied to the announced sales price of a property to derive a “market capitalization rate”.