Calculation details
Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.
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Use this result
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What does this calculator estimate?
An APR calculator shows the true cost of a loan including fees. Enter the amount, stated rate, term, and fees to see the APR and effective rate.
- APR includes fees; the stated rate doesn't
- Effective rate = (1 + APR/12)^12 − 1
- Compare loans by APR, not the headline rate
What APR reveals
The stated interest rate ignores upfront fees. APR folds fees into the rate so you can compare loans honestly: a loan with a lower rate but heavy fees can be more expensive than one with a higher rate and no fees.
Limitations to watch for
APR assumes the loan runs to term — refinancing or early payoff changes the true cost. APR is an annualized rate with monthly compounding; the effective annual rate (EAR) converts it for comparison with other investments. APR excludes late fees and some charges.
How to use it in practice
When comparing offers, put the same amount, term, and each lender's fees into the tool and compare APRs. Pay attention to how fees are financed (deducted from proceeds vs added to balance).
- Enter the loan amount, stated rate, and term.
- Enter the fees.
- Compare the APR across lenders.
APR vs. interest rate
The interest rate is the cost of borrowing the principal; APR adds lender fees and points, expressing the true annual cost. A loan at 6 percent with $3,000 in fees has an APR around 6.4 percent. The calculator converts rate, fees, term, and compounding into the effective APR.
Why APR exists
APR standardizes comparison: two loans with the same rate but different fees have different real costs. Truth-in-Lending requires lenders to quote APR so borrowers compare apples to apples. The calculator reproduces that standard for any loan terms.
Compounding changes the effective rate
The effective annual rate also depends on compounding frequency: a 12 percent nominal rate compounded monthly has an EAR of about 12.68 percent. Credit cards compound daily, pushing the effective rate slightly higher. The calculator shows both the APR and the compounded effective rate.
A worked example
A $20,000 auto loan at 5 percent over 60 months with a $500 origination fee: the payment is based on the rate, but the fee raises the effective cost to about 5.8 percent APR. The calculator surfaces that gap, which is exactly what lenders prefer to hide.
When APR misleads
APR assumes the loan runs to term; pay it off early and the effective cost per month rises. Adjustable loans quote an APR that can shift later. Use APR for comparison, but model your actual payoff timeline for the real cost.
How this calculator works
Formula
APR = the rate that makes the loan's present value (principal minus fees) equal to the payment stream. Effective rate = (1 + APR ÷ 12)^12 − 1 for monthly compounding. Fees raise the APR above the stated rate.
Worked example
A $10,000 loan at 6% for 36 months with $500 in fees: the APR is higher than 6% because you receive $9,500 but repay a 6% amortization schedule.
Assumptions to verify
- The loan is amortized monthly.
- Fees are deducted from the loan proceeds.
- The loan runs to full term.
Frequently asked questions
What is APR?
The annual percentage rate — the true yearly cost of a loan including fees, expressed as a rate. It's the number to use when comparing loans.
Why is APR higher than the stated rate?
Fees are added to the cost but you receive less money, so the effective rate rises. The APR captures that.
What is the effective annual rate?
The EAR converts a nominal rate with monthly compounding into the equivalent yearly rate: (1 + r/12)^12 − 1.
How do I compare loans?
Use the same amount and term, include each lender's fees, and compare the APRs — not the headline rates.
Do APRs include everything?
No — late fees, prepayment penalties, and some charges are excluded by regulation. Read the loan terms.
What if I pay off early?
APR assumes you hold the loan to term. Paying early changes the real cost — refinance break-even math applies.
What's the difference between APR and APY?
APR is a borrowing cost; APY is a deposit yield. Both annualize, but APY includes compounding effects.
What is the difference between APR and interest rate?
APR includes fees and points; the interest rate is just the borrowing cost on the principal.
How do I calculate APR?
APR is the rate that makes the payments equal to the loan amount minus fees over the term.
Does compounding affect APR?
Yes — more frequent compounding raises the effective annual rate above the nominal APR.
Why do lenders quote APR?
Truth-in-Lending requires it so borrowers can compare loans with different fees.
Cite this tool
BoringToolsKit. “APR & Effective Interest Calculator.” boringtoolskit.com/apr-effective-interest-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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