How the Loan Interest Calculator works
Estimate total interest on a loan. Adjust the inputs above, then use the calculate button to generate a fresh estimate based on the numbers you entered.
The result is designed to give you a quick planning number, plus a short breakdown of the major figures behind it. You can reset the form at any time and try a different scenario.
When to use this calculator
Use this loan interest calculator to estimate how much interest a loan may cost over the full repayment term. It is useful for seeing the hidden cost behind a monthly payment.
Formula
Total interest = total of payments - loan amount
- Loan amount is the principal borrowed.
- Rate and term estimate the monthly payment.
- Total payments are the monthly payment multiplied by the number of months.
Worked example
For a $30,000 loan at 7.5% over 5 years, the calculator estimates the monthly payment and subtracts the original loan amount to show total interest.
Common mistakes
- Looking only at the payment and missing the total interest.
- Ignoring fees that may also add to borrowing cost.
- Assuming every payment goes mostly to principal early in the loan.
FAQs
Why is interest higher on longer terms?
Longer terms keep the balance outstanding for more time, so interest has more months to accumulate.
Can extra payments reduce interest?
Often yes, if your lender applies them to principal and does not charge prepayment penalties.
Does this show an amortization schedule?
No. It gives total payment and interest estimates, not a month-by-month schedule.