Calculation details
Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.
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What does this calculator estimate?
APR calculator: convert nominal interest plus fees into fee-adjusted APR and effective interest rate so you can compare true loan cost. Free, no signup.
Why is APR higher than the interest rate on the same loan?
APR folds fees and certain closing costs into the rate, expressing the loan's total cost as a single yearly figure. A 6.5% rate with a 2% origination fee produces an APR above 6.5% because you are paying interest on money you never received. The gap widens with fees and shrinks the longer you hold the loan, which is why comparing APRs beats comparing rates for hold-and-pay loans.
When is comparing APRs misleading?
APR assumes the loan runs to term. If you expect to sell, refinance, or pay off early, a loan with high fees and a low rate looks better by APR than its early-exit reality, and the reverse holds for low-fee loans. For expected short holds, compare total costs at your realistic payoff date instead of the standardized figure.
How this calculator works
Formula
The payment uses the stated nominal rate and financed principal. Estimated APR solves the monthly discount rate that makes the payment stream equal net proceeds after fees, then annualizes that monthly rate. Effective annual rate compounds the solved monthly rate for twelve months.
Worked example
A $10,000, 36-month loan at 8% with $300 deducted upfront has a $313.36 payment, about 10.08% estimated fee-adjusted APR, 10.56% effective annual rate, and roughly $1,581 total finance cost relative to net proceeds.
Assumptions to verify
- Payments are level, monthly, and made at the end of each period.
- Fees are either deducted from proceeds or added to financed principal according to the selected option.
- The estimate excludes insurance, irregular payment timing, prepayment, late charges, and jurisdiction-specific disclosure rules.
Frequently asked questions
Why is estimated APR above the stated rate?
Fees reduce proceeds or increase financed principal while payments remain higher, increasing the implied borrowing cost.
What is effective annual rate?
It compounds the solved monthly cost over twelve periods, unlike the nominal annualized APR estimate.
Will this exactly match a lender disclosure?
Not necessarily. Official calculations can use regulated charge definitions, exact dates, rounding, insurance, and other timing conventions.
Cite this tool
BoringToolsKit. “APR & Effective Interest Calculator.” boringtoolskit.com/apr-effective-interest-calculator/ (reviewed July 2026). Free to reference in articles, syllabi, and answer posts with a link.
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