APR Calculator
Free APR calculator. Convert a loan's note rate and upfront fees into the true annual percentage rate disclosed under the Truth in Lending Act.
APR Calculator
Background.
An APR calculator converts the two numbers a lender quotes you — the note interest rate and the upfront finance charges — into the single number that lets you honestly compare one loan offer against another: the annual percentage rate. The APR is not a marketing figure. It is a federally-mandated disclosure under the Truth in Lending Act (15 U.S.C. § 1601 et seq.) and Regulation Z (12 C.F.R. Part 1026), and it answers a very specific question — what annual rate, charged on the net cash you actually receive at closing, produces the same stream of monthly payments the lender is going to collect from you? The math is iterative because there is no closed-form solution; this calculator runs the same Newton-Raphson iteration that lender APR-disclosure software uses internally, converging on the APR to four decimal places. Enter the gross loan amount the lender will originate, the note rate from your promissory note, the term in years, and the sum of all upfront finance charges — origination fees, discount points, mortgage broker fees, mortgage insurance premiums, and any other charges that Regulation Z classifies as a prepaid finance charge — and you will get back the APR, the scheduled monthly payment, the total all-in cost of the loan over its full term, and the effective fee rate as a percentage of the loan amount.
The headline-rate-versus-true-cost distinction is the entire reason APR exists. A lender can advertise a 5.00% rate on a $200,000 thirty-year mortgage and bury $4,000 in origination and points at closing; another lender can advertise 5.25% on the same loan with zero upfront fees. The first loan's note rate is 25 basis points lower but its APR works out near 5.17%, which means the second offer at 5.25% is actually the cheaper loan over the full term once you account for the cash you paid at closing. The Consumer Financial Protection Bureau's standardized Loan Estimate form, mandated by the TILA-RESPA Integrated Disclosure rule, forces every U.S. lender to display the APR on page 3 alongside the note rate on page 1 precisely so consumers can run this comparison without doing the math themselves.
The calculator also makes the APR-versus-APY distinction explicit. APY (annual percentage yield) describes how interest compounds upward on a deposit account — savings, certificates of deposit, money market funds — and obeys a different formula entirely (APY = (1 + r/n)^n − 1, where r is the nominal rate and n is the compounding frequency). APY belongs to deposits; APR belongs to loans. They are not interchangeable, and a lender quoting APY on a credit product is either confused or selling something. The APR is also not the same thing as the effective annual rate (EAR), which compounds the APR itself to reflect how interest accumulates on the unpaid balance. For a monthly-compounding loan, EAR = (1 + APR/12)^12 − 1, which lifts a 5.17% APR to about 5.29% EAR — but Regulation Z does not require lenders to disclose EAR, and the APR alone is the legally-mandated comparison metric.
A few honest limits of APR. It assumes you hold the loan to maturity. If you sell the house in year five and pay off a thirty-year mortgage, the upfront fees were amortized over five years not thirty, and your effective cost was much higher than the disclosed APR — the same loan, looked at honestly, was a worse deal than the comparison suggested.
APR also does not capture prepayment penalties, balloon payments, adjustable-rate features after the initial fixed period, or the discount-point trade-off where you pay more cash upfront to buy down the note rate. For ARMs, lenders disclose a fully-indexed APR assuming current index values, which can swing materially over the life of the loan. Use this calculator as the right first comparison between fixed-rate offers; for ARM and balloon structures, also compare worst-case payment scenarios.
What is apr calculator?
The annual percentage rate (APR) is a standardized measure of the cost of credit, expressed as a yearly rate, that includes both the periodic interest charged on the loan and the upfront finance charges paid at closing. It was created by the Truth in Lending Act of 1968 and is governed today by Regulation Z, 12 C.F.R. Part 1026, which the Consumer Financial Protection Bureau enforces. The APR is mathematically defined as the rate that, when applied to the net amount the borrower actually receives at closing (the loan amount minus the prepaid finance charges), discounts the future stream of scheduled loan payments back to that net amount. In equation form, it is the rate r that satisfies Net Proceeds = Σ Payment_t / (1 + r/12)^t for t = 1 to n monthly periods. Because there is no algebraic solution for r, every modern APR disclosure is generated by numerical iteration — Newton-Raphson, secant method, or bisection — converging on the rate to four-decimal precision. Regulation Z is explicit about which closing costs qualify as prepaid finance charges that enter the APR calculation: loan origination fees, discount points, mortgage broker fees, mortgage insurance premiums (private MI on conventional loans and the FHA up-front MIP), prepaid interest from closing to the first payment date, and certain third-party fees the lender requires. Costs that do not enter the APR calculation include title insurance, appraisal fees, credit report fees, government recording fees, and homeowners insurance — Regulation Z classifies these as bona fide third-party charges rather than finance charges. The APR's purpose is comparative: it normalizes loan offers with different fee structures so the borrower can rank them by true cost, which is why every consumer credit disclosure since 1968 has been required to display it with equal prominence to the note rate.
How to use this calculator.
- Enter the gross loan amount the lender will originate. This is the face value on the promissory note, not the cash you will actually receive at closing if origination fees are netted out.
- Enter the note interest rate from your loan agreement or Loan Estimate page 1. This is the rate used to calculate the contractual monthly payment — never the APR itself.
- Enter the term in years. Thirty for a standard mortgage, fifteen for a fast-payoff mortgage, five to seven for most auto loans, two to seven for unsecured personal loans.
- Enter the total upfront finance charges. On a Loan Estimate this is the sum of origination charges (page 2 section A), discount points if any, mortgage insurance premiums financed at closing, and any lender or broker fees Regulation Z classifies as prepaid finance charges. Exclude title insurance, appraisal, credit report, and recording fees.
- Read the APR — the headline output. Compare it directly to the APR on any competing loan offer over the same term. The lower APR is the cheaper loan if you hold it to maturity.
- Use the effective fee rate as a sanity check. Heavy upfront fees on a short loan inflate the APR sharply (a $4,000 fee on a five-year loan adds far more APR than the same fee spread over thirty years), which is why APR alone can mislead when you plan to refinance or sell early.
The formula.
The note-rate monthly payment is calculated first using the standard amortizing-loan formula M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the gross loan amount, r is the periodic monthly note rate (annual rate ÷ 100 ÷ 12), and n is the total number of monthly payments (term in years × 12). The APR is then solved as the rate i that satisfies (P − F) = M × [1 − (1 + i/12)^(−n)] / (i/12), where F is the upfront finance charges. There is no algebraic solution; the calculator uses Newton-Raphson iteration starting from the note rate as the initial guess, evaluating the present-value function and its analytic derivative each iteration, terminating when successive estimates differ by less than 1e-8. Convergence is reliable for any realistic loan because the function is monotonically decreasing in i. Total cost of loan is M × n + F. Effective fee rate is F / P expressed as a percentage — useful for comparing the fee load across offers before running the full APR math.
A worked example.
Take a $200,000 thirty-year mortgage at a 5.00% note rate with $4,000 in upfront origination fees and discount points — a realistic 2026 conforming-loan profile. The contractual monthly payment lands at $1,073.64, computed against the full $200,000 principal at the 5.00% rate. Over 360 payments the lender collects $386,511.57 in scheduled payments, and you have already handed over $4,000 at closing, so the all-in total cost of the loan is $390,511.57. The APR works out to roughly 5.17% — seventeen basis points above the note rate — because the calculator solves for the rate that, applied to the $196,000 you actually netted at closing, produces those same $1,073.64 monthly payments over thirty years. A competing lender quoting 5.25% with zero upfront fees would have an APR of exactly 5.25%, which means the second offer is the cheaper loan over the full thirty-year term despite carrying a higher headline rate. The effective fee rate of 2.00% on this loan is the sanity check — if those same $4,000 in fees sat on a five-year personal loan instead, the effective fee rate would still be 2.00% but the APR impact would be roughly five times larger because the fees would amortize over sixty payments instead of three hundred and sixty.
Frequently asked questions.
What is the difference between APR and the note interest rate on a loan?
Why is APR the only honest way to compare loan offers?
What fees are included in the APR calculation and which are excluded?
What is the difference between APR and APY?
How is APR calculated mathematically?
Does APR account for prepayment penalties or early payoff?
Why does adding upfront fees make a short loan's APR jump much more than a long loan's?
Is APR the same as the effective annual rate (EAR)?
How does APR work for adjustable-rate mortgages (ARMs)?
Where does the Truth in Lending Act mandate APR disclosure, and what happens if a lender gets it wrong?
References& sources.
- [1]Consumer Financial Protection Bureau — What is the difference between a mortgage interest rate and an APR? (official explainer of APR vs note rate)
- [2]Consumer Financial Protection Bureau — Loan Estimate explainer (TILA-RESPA Integrated Disclosure, where APR is mandated to appear on page 3)
- [3]Federal Reserve / Code of Federal Regulations — Regulation Z, 12 C.F.R. Part 1026 (full Truth in Lending implementing regulation, including § 1026.4 finance charge definition and Appendix J APR calculation method)
- [4]Truth in Lending Act — 15 U.S.C. § 1601 et seq. (statutory basis for APR disclosure)
- [5]IRS Publication 936 (2025) — Home Mortgage Interest Deduction (clarifies which mortgage interest is deductible; relevant when assessing after-tax effective cost vs APR)
- [6]Federal Trade Commission — Truth in Lending Act overview and consumer rights
- [7]Bankrate — APR vs interest rate methodology and worked examples
- [8]Consumer Financial Protection Bureau — Compliance Guide to Regulation Z (operational guidance for lenders on calculating and disclosing APR)
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