A decision tool, not just an answer.
Use this calculator when you know the amount borrowed, annual interest rate, and repayment term for a personal loan, auto loan, or other fixed installment loan. It helps compare offers on a consistent monthly-payment and total-cost basis.
- Checking whether a proposed monthly payment fits your budget.
- Comparing a longer term with a lower payment but higher lifetime interest.
- Estimating the effect of a different loan amount or quoted annual rate.
Formula and calculation method.
M = P × [i(1 + i)ⁿ] ÷ [(1 + i)ⁿ − 1]M is the monthly payment, P is the amount borrowed, i is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the number of monthly payments. The total paid is M × n, and total interest is total paid minus P.
Zero-rate case: For a true 0% loan, no interest factor is needed: monthly payment = amount borrowed ÷ number of months.
See the result in context.
$24,000 borrowed at 7.2% for 5 years
Working: 60 monthly payments using a 0.6% monthly rate
Result: $477.50 per month; $28,649.80 total paid; $4,649.80 interest
Interpretation: The payment is below $500, but interest adds almost 19.4% of the original amount over five years.
$35,000 borrowed at 5.5% for 4 years
Working: 48 fixed monthly payments using the amortization formula
Result: $813.98 per month; $39,070.88 total paid; $4,070.88 interest
Interpretation: The shorter term raises the monthly commitment while limiting the time over which interest accrues.
$18,000 borrowed at 0% for 3 years
Working: $18,000 ÷ 36 months
Result: $500 per month; $18,000 total paid; $0 interest
Interpretation: At 0%, the payment simply spreads the principal evenly, assuming there are no fees or deferred-interest conditions.
Assumptions and common mistakes.
What the estimate assumes
- The interest rate is fixed and payments are made monthly for the full term.
- Every scheduled payment is made on time and no extra principal payments are added.
- The quoted rate is treated as a nominal annual rate divided into 12 monthly periods.
- The calculator assumes a standard fully amortizing loan with no balloon payment.
Mistakes to avoid
- Entering the purchase price instead of the amount actually financed.
- Comparing monthly payments without comparing total interest and total repayment.
- Treating an advertised payment as complete when origination fees or add-ons are financed separately.
- Using an introductory or variable rate as though it were fixed for the full term.
What unusual inputs mean.
The result divides the principal evenly across the monthly payments and reports zero interest.
The mathematical payment is zero. Real lenders may still charge minimum fees, so confirm the offer terms.
Short terms can produce a high monthly payment even when they reduce total interest.
How to use this calculator.
- Enter the amount you expect to borrow, excluding any down payment paid directly.
- Enter the quoted annual interest rate. Use 0 only for a genuinely interest-free loan.
- Enter the repayment term in years, then review both the monthly payment and lifetime interest.
- Change one input at a time to compare offers—for example, keep the amount and rate fixed while testing a shorter term.
What the estimate leaves out.
This is a planning estimate, not a lender disclosure. It excludes origination fees, late fees, optional products, changing rates, irregular first-payment periods, prepayments, and lender-specific rounding. Review the APR and official repayment schedule before accepting a loan.
Questions people ask.
How is a loan payment calculated?
A standard fixed-rate payment amortizes the amount borrowed over equal monthly payments. Each payment covers that month’s interest and reduces principal; the interest share generally falls as the balance declines.
What is the difference between interest rate and APR?
The interest rate drives the interest portion of the payment. APR can also reflect certain lender fees and is designed for comparing borrowing costs. This calculator uses the entered interest rate, not a fee-adjusted APR calculation.
Does a longer loan term lower the payment?
Usually yes, because repayment is spread across more months. A longer term commonly increases total interest even though the monthly payment is lower.
Can I use this for an auto or personal loan?
Yes, when the loan has a fixed rate, fixed term, and equal monthly payments. Enter the financed amount rather than the item’s full purchase price if you are making a down payment.
Are loan fees included?
No. Add any financed fee to the loan amount if you want a rough payment estimate, but use the lender’s disclosure for the exact APR and total of payments.
What happens if I make extra payments?
Extra principal payments can shorten the payoff time and reduce interest, but this calculator models only the scheduled payment. Check whether your lender applies extra amounts to principal and whether any prepayment penalty applies.
Why might a lender quote a slightly different payment?
Differences can come from payment dates, compounding conventions, financed fees, lender rounding, or an APR that is not the same as the note rate entered here.