Annual Percentage Rate (APR) is an expression of the effective interest rate that will be paid on a loan, taking into account one-time fees and standardizing the way the rate is expressed. The aim of using APR is to calculate a total cost of borrowing. APR is intended to make it easier to compare lenders and loan options. The APR is likely to differ from the "note rate" or "headline rate" advertised by the lender. The concept of APR can be generalized. For example lenders use the same concept to calculate their total earnings on loans and for determining their margin on the loan.

Consumers can use the APR concept to compare savings accounts and calculate the earnings on a savings account, taking transaction costs into account. In the US and the UK, lenders are required to disclose the APR before the loan (or credit application) is finalized. APR is a term used with regards to deposit accounts as well. However, when dealing with deposit accounts, Annual percentage yield or APY is the number to be quoted to consumers for comparison purposes. The truth is that APR is a very poor way to comparison shop for a mortgage and can cause borrowers to make costly decisions. APR was created to provide a way for borrowers to account for costs associated with the mortgage. This sounds good because it may not be very easy to choose between a loan with a lower rate and higher fees or a loan at a higher rate with low fees.

The problem is that the APR calculation is based on bad assumptions. First, APR assumes zero inflation and that the value or buying power of a dollar today will be exactly equal to the value of a dollar 10, 20, or even 30 years from now. Next, the APR calculation assumes that the mortgage will never be pre-paid or paid. That means no refinancing or selling the home, which is highly unlikely since the average life of a home mortgage loan is less than four years.

Just think about your own loans: Is it rare to see the same loan in place for even five years-forget 30 years? The APR calculation does not consider the value of the money used for fees. So if you spent thousands of dollars in points or fees to get a lower rate, the APR calculation does not give any value to the money if it wasn't spent on closing costs. Finally, APR does not take tax consequences into consideration. This can be significant, since higher fees on the mortgage may not be deductible, while the higher interest rate typically is deductible. Moreover, APR can be easily manipulated by bad lenders, making it totally worthless.