More commonly called APR, Annual Percentage Rate is a government-mandated mortgage comparison tool. It measures the total cost of borrowing over the life of a loan into dollars-and-cents. A loan's APR is printed in the top-left corner of the Federal Truth-In-Lending Disclosure, as shown above. When quoting an interest rate, loan officers are required by law to disclose a loan's APR, too. APR is meant to simplify the process of choosing between two or more loans. The theory is that the loan with the lowest APR is the "best deal" for the applicant because the loan's long-term costs are lowest. However, the loan with the lowest APR isn't always best. APR makes assumptions in its formula that can render it moot.