Loan Calculator
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How it works
Use this loan calculator when you need a fixed monthly payment and a total-interest estimate for an amortizing installment loan—personal loans, auto loans, or similar products with a stated APR and term. The math is the classic amortizing payment formula: equal payments that clear both interest and principal by the final due date.
Enter the amount you will actually borrow (after down payment or trade-in if relevant), the APR as a percent, and the term in months or years. Compare two offers by holding the amount constant and swapping rate and term: a slightly lower rate with a much longer term can still cost more interest overall. Watch origination fees—if a fee is financed, add it to principal; if it is paid upfront, treat it as cash-to-close rather than part of the payment formula.
This model assumes a fixed rate, no balloon payment, and no early-payoff penalty math. Variable-rate loans, interest-only periods, and deferred interest change the payment path. If you plan to pay extra, re-run with a higher monthly amount or shorter term to estimate interest saved rather than guessing from the original schedule.
Input guidance
- Use the amount you will actually finance after down payment or trade-in.
- Enter APR, not only a marketing “as low as” teaser rate.
- Match the term to the contract length; longer terms hide interest in a lower payment.
The formula
A fixed-rate loan amortizes with M = P · r · (1+r)^n / ((1+r)^n − 1): equal monthly payments of principal plus interest so the balance reaches zero at the end of the term. P is the amount borrowed, r the monthly rate, n the number of payments.
Worked example
Borrow $20,000 at 9% APR over 5 years: r = 0.0075, n = 60. The monthly payment is about $415, and total interest over the loan is roughly $4,910.
More examples to test
- $15,000 personal loan at 11% for 36 months vs 60 months: compare payment vs total interest.
- Add a $300 financed origination fee to principal and re-check the payment.
How to interpret results
Rank offers by total interest and fees for the same borrowed amount, not by payment alone. Confirm whether fees are financed or paid upfront.
When this can be inaccurate
Variable rates, deferred interest, balloons, and prepayment penalties are outside this fixed-amortization model.
Change history
- July 2026: Added comparison guidance for rate/term tradeoffs and financed fees.
- June 2026: Amortizing payment math reviewed against reference cases.
Site-wide corrections also appear on the corrections log.
Find the best personal loan for you
Multiple lenders, one form.
Frequently asked questions
What counts as an amortizing loan?+
Most personal loans, auto loans, and mortgages amortize: each payment is split between interest on the remaining balance and principal, with the principal share growing over time.
Why is so much early payment interest?+
Interest is charged on the outstanding balance, which is largest at the start. Early payments are mostly interest; later payments are mostly principal.
Does paying extra help?+
Yes. Extra payments go straight to principal, shrinking the balance future interest is charged on, which shortens the term and lowers total interest.
Is a lower payment always better?+
Not if it comes from a much longer term that increases total interest. Compare interest totals and how long you will carry the debt.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.
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