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Loan and financing calculator

Work out the payment, interest and true annual cost of a loan with fixed payments or constant principal, grace period and fees. See how rate and term change the cost, and whether refinancing with another lender pays.

Educational simulation. Not investment advice. Results are estimates based on the data you enter and do not replace advice from a qualified professional.

Reviewed on Oct 31, 2026
Ready-made examples
Amounts
Amount financed—
Term and repayment

Repayment method

Interest

Fees

Upfront: origination, appraisal and registration. Monthly: account or service fees and insurance billed with each payment.

Your inputs stay only on this browser and are not sent anywhere. Untick to delete them.

First payment
—
Total paid
—
Total interest
—
True annual cost
—
Amount financed
—
For every dollar received, how much you pay back

    What is inside each payment Fixed

    Choose the method below. Principal reduces the debt; interest and fees are the cost.

    Tap the chart to see the values.

    Where your money goes

    Cumulative amounts paid over time, against the balance still owed.

    Tap the chart to see the values.

    Fixed payment or constant principal?

    Payment month by month with both methods, same assumptions.

    Tap the chart to see the values.

    What if the rate or the term change?

    Your simulation is in the center. Tap a cell to simulate that case.

    cheapermore expensive

    Year by year

    When refinancing pays off

    Savings on the payments added up over time, against the switching costs. Where they cross is the break-even month.

    Tap the chart to see the values.

    Current loan × new offer

    Next step

    Take this page’s results to another calculator with the fields already filled in.

    Is refinancing your mortgage worth it? →

    The summary lists your inputs, results, formulas, assumptions and sources. The full report also includes the charts and interpretations, in color. In the print dialog, choose Save as PDF.

    Method, assumptions and sources

    Formulas

    Fixed payment = balance × i ÷ [1 − (1 + i)^−n]
    Constant principal: principal = balance ÷ n; interest = month’s balance × i
    Fees added to the loan: amount financed = amount received + upfront fees
    True annual cost: rate r such that Σ payment_m ÷ (1 + r)^m = net amount received; yearly = (1 + r)^12 − 1
    Refinancing: savings = Σ current payments − Σ new payments − switching costs

    Assumptions and limits

    • The official cost and terms are those in the lender’s disclosure; approval depends on each lender’s credit review.
    • Monthly payments with compound interest on the outstanding balance; fixed rate. Variable rates, escrow, property taxes and prepayment penalties are not included.
    • Refinancing uses fixed payments on the same balance; “keep the payment” pays off sooner with the same payment. Switching costs paid upfront.

    Official sources and references

    Frequently asked questions

    What does this loan calculator show?

    The monthly payment, the total you pay back, total interest and the true annual cost including fees, for fixed payments or constant principal. It also compares the two methods, tests other rates and terms and, in “Refinance” mode, shows whether moving your loan to a cheaper lender pays.

    Where do I get each number?

    The rate, term and fees come from the lender’s offer or loan estimate. Choose whether the rate you type is monthly or yearly. Upfront fees are origination, appraisal or registration charges; monthly fees are account or service charges and insurance billed with each payment.

    How do I read the default example?

    A $30,000 car with $5,000 down, 60 months at 7.5% a year and $500 of fees added to the loan gives a fixed payment of about $507.99. The cards show the total paid (about $30,479), total interest (about $4,979) and the true annual cost, about 8.40%, above 7.5% because of the fees.

    Fixed payment or constant principal: which costs less?

    Constant principal pays less interest, because the balance falls faster. A fixed payment is lower at the start and predictable, but costs more in total. The comparison card shows the difference for your numbers.

    What is the true annual cost?

    It is the yearly rate that equates the money you actually receive with all payments, including fees. It is the right number to compare offers. U.S. loan disclosures show a similar figure, the APR, usually quoted as a monthly rate times 12.

    When is refinancing worth it?

    When the savings on the payments exceed the switching costs before you expect to pay off or refinance again. In the default refinance example, moving $18,000 with 42 months left from 9.9% to 6.9% a year lowers the payment by about $23 and saves about $631 after $350 of costs, breaking even in month 15. Watch out for a longer term that hides the cost.

    What are the limits of this simulation?

    It assumes a fixed rate, monthly payments and no late fees. Variable-rate loans, mortgages with escrow and taxes, and prepayment penalties are not modeled. Always check the lender’s official disclosure before signing.

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    How to know the real cost of a loan

    The interest rate is only part of what a loan costs. Origination and appraisal fees, monthly service charges and insurance billed with the payments all add up. The number that captures everything is the true annual cost: the yearly rate that equates the money you actually receive with every payment you make. In the U.S. the closest legal figure is the APR on your loan disclosure.

    Fixed payment or constant principal

    With a fixed payment (the usual amortizing loan), every payment is the same; early on most of it is interest and the principal part grows over time. With constant principal, the debt falls by the same amount every month: payments start higher and decrease, and total interest is lower. For a $25,000 car loan at 7.5% a year over 60 months, the fixed payment is about $498 a month.

    What makes a loan cheaper

    A lower rate, a shorter term and a bigger down payment. Stretching the term lowers the payment but multiplies the interest: the sensitivity table shows how much. Paying upfront fees in cash instead of adding them to the loan also saves interest on the fees themselves.

    Refinancing

    If rates fell or your credit improved, moving the balance to a cheaper lender can save a lot. Use the “Refinance” mode: type the balance, the months left, the current and the new rate and the switching costs. The calculator shows the savings and the break-even month, when the lower payments have paid for the costs.