What is APR?
The annual percentage rate folds a lender’s charges back into the interest rate, so two offers can be compared on one number. Here is what it includes, how it is calculated, and where it stops being trustworthy.
What the APR includes
The APR is the interest rate plus the lender’s own charges, spread back across the life of the loan and expressed as a yearly rate. Regulation Z calls those charges the finance charge: anything you pay as a condition of getting the credit.
Typically inside the APR:
- discount points and origination fees
- underwriting, processing and document preparation charges
- mortgage insurance premiums
- prepaid interest from closing to the first payment
Typically outside it:
- appraisal, credit report and home inspection fees
- title insurance and settlement charges you may shop for
- recording fees and transfer taxes
- property taxes, homeowners insurance, HOA dues
The dividing line is not “did it appear on the closing statement” but “did the lender require it as part of extending the credit”. Two lenders can classify a borderline fee differently, which is one reason APRs from different lenders are comparable but not perfectly so.
How it is calculated
Appendix J to Regulation Z specifies the actuarial method. In plain terms:
- Start with the amount financed — the loan amount minus the prepaid finance charges you are paying up front.
- Take the payment stream the note actually requires, which is calculated on the full loan amount at the note rate.
- Find the single rate at which those payments, discounted back to closing, equal the amount financed.
That rate is the APR. You are borrowing less than the face amount but repaying as though you borrowed all of it, so the effective rate is higher than the note rate. The bigger the up-front charges, the wider the gap.
Because the calculation solves for a rate rather than applying a formula, it has no closed-form answer — lenders and regulators alike compute it numerically. Disclosures are considered accurate within one-eighth of one percentage point.
Where the APR misleads
It assumes you keep the loan to term. This is the big one. The APR spreads your up-front costs over 30 years. Sell or refinance in year five and you paid those costs over five years instead, making your true annualized cost far higher than the disclosed APR. Points look good on a 30-year APR and often lose money in real life, where the median mortgage lasts under a decade.
It cannot compare different terms. A 15-year and a 30-year loan quoted at the same APR are not equivalent purchases.
On adjustable-rate loans it is a projection. The APR assumes the index stays where it is today. It will not.
It says nothing about the costs outside it. A lender with a low APR and expensive third-party requirements can cost more at the table than one with a higher APR.
The APR is the best single number available for comparing fixed-rate loans of the same term that you intend to hold. Outside those conditions, compare total cost over the horizon you actually expect — which is what comparing two offers does.