Finance & Money
Loan Calculator
Estimate any fixed-rate loan payment, test extra principal payments, or work backward from a monthly payment to the loan amount you can afford.
Monthly payment
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- Total interest
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- Total paid
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- Payoff time
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Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What this loan calculator can solve
| Mode | Use it when | Output |
|---|---|---|
| Monthly payment | You know loan amount, APR, and term | Payment, interest, payoff time, and extra-payment savings |
| Loan amount from payment | You know your monthly budget | Maximum loan amount for that payment |
Loan payment formula
P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. This assumes a fixed-rate fully amortizing loan.
How extra payments help
Extra monthly principal payments reduce the balance faster. That shortens the payoff time and lowers total interest because future interest is charged on a smaller balance.
Worked examples
$25k auto loan, 6.5%, 5 years
Standard fixed loan
Monthly payment
$489.15
$25k loan with $100 extra
Extra principal payoff impact
Monthly payment
$589.15
$500/month at 6.5% for 5 years
Reverse-solve loan amount
Monthly payment
$500.00
Frequently asked questions
Does this work for auto loans?+
Yes. It works for any fixed-rate amortizing loan, including auto, personal, and many student loans.
Does this include fees?+
No. Add origination or dealer fees to the loan amount if they are financed.
What is APR?+
APR is the annualized borrowing cost including certain fees. If you are comparing offers, APR is usually better than the stated interest rate.
Do extra payments always save interest?+
Usually, yes, if they are applied to principal and there is no prepayment penalty. Check your lender's payment rules.
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Last updated: May 8, 2026