Loan Calculator
Estimate monthly payment, total interest, payoff impact, and amortization for a fixed-rate installment loan.
Last reviewed: June 2026Quick Answer
A loan's monthly payment depends on the amount borrowed, the interest rate, and the term. Using the standard amortization formula, a $20,000 loan at 6% over 5 years costs about $387 per month. Enter your amount, rate, and term above to see the monthly payment, total interest, and payoff schedule.
What this loan calculator estimates
This loan calculator estimates the scheduled payment for a fixed-rate installment loan. Enter the loan amount, annual interest rate, term in years, and any extra monthly principal payment. The page returns the monthly payment, total interest, total cost, optional interest savings from extra payments, optional time savings, and a month-by-month amortization schedule.
The calculator is intentionally narrow. It models principal and interest only. It does not add origination fees, credit insurance, closing costs, late fees, prepayment penalties, taxes, escrow, servicing fees, or variable-rate adjustments. If a lender rolls fees into the balance, include those fees in the loan amount. If fees are paid out of pocket, add them separately when comparing total cost.
Formula used on this page
For a positive interest rate, the monthly payment is calculated with the standard amortization formula: M = P x [r(1 + r)^n] / [(1 + r)^n - 1]. In that formula, P is the loan amount, r is the annual rate divided by 12, and n is the number of monthly payments. If the rate is 0%, the calculator divides the loan amount evenly across the term.
The extra-payment section uses the scheduled payment first, then adds the extra amount to principal after that month's interest is calculated. Because future interest is charged on a lower balance, extra payments can save interest even when the scheduled payment itself does not change. The amortization table shows the same logic one month at a time.
Worked default example
With the default inputs, a $25,000 loan at 6.5% for 5 years produces a scheduled payment of about $489.15 per month. If every scheduled payment is made, total interest is about $4,349.22 and total cost is about $29,349.22. Adding $100 per month in the extra payment field lowers the modeled interest by about $865.44 and pays the loan off 11 months sooner.
Those numbers are useful for comparing payment pressure and interest cost, but they are not a complete lending disclosure. A lower payment can come from a lower rate, a longer term, or both. A longer term usually lowers monthly cash flow but can increase total interest because the balance remains outstanding for more months.
How to compare loan offers
- Monthly payment: The amount due each month under the modeled fixed-rate schedule.
- Total interest: Interest paid over the full term if no extra principal is added.
- Total cost: Principal plus scheduled interest on this page, excluding separate fees.
- APR and fees: APR can include mandatory loan fees, while the note rate may be what drives the payment calculation.
- Prepayment terms: Extra payments help only if the loan lets you apply them to principal without a costly penalty.
Sources and further reading
For consumer context, see the CFPB explanation of loan interest rate versus APR and CFPB Truth in Lending disclosure guidance. Those resources explain why APR, finance charges, payment amount, and total loan cost should be compared from the written offer, not just from the advertised payment.