Interactive financial calculator
Loan Amortization Calculator
Estimate a generic loan payment and amortization schedule, then compare the payoff time and interest with optional extra principal payments.
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- No account required
- Inputs stay in your browser
Methodology & Assumptions
How this estimate is calculated
Amortization: scheduled payment = P × r ÷ [1 − (1 + r)−n], where r is nominal APR ÷ 12 and n is the term in months. Interest is allocated first, followed by the scheduled payment, recurring extra principal, and any one-time extra in its selected payment month.
Illustrative result: figures are rounded for display after calculations use full numeric precision. Actual results may differ.
Currency: dollar symbols are a display convention. Enter every monetary amount in one consistent currency; the calculator does not convert currencies or apply jurisdiction-specific tax rules.
How to Use This Loan Amortization Calculator
Enter a generic loan principal, nominal APR, and monthly term. Optional recurring and one-time extra principal payments create an accelerated schedule alongside the original schedule. The result is an illustrative amortization estimate, not a lender quote.
Read Loan Amortization with Extra Payments for the formula, timing convention, and detailed example.
Scheduled Payment Formula
For principal P, monthly rate r, and n payments, the scheduled payment is P × r ÷ [1 − (1 + r)−n]. The monthly rate is nominal APR divided by 12. At 0% APR, scheduled payment is principal divided evenly across the term.
Payments occur at the end of each monthly period. Interest is allocated first. The scheduled payment follows, then recurring extra principal, then the one-time extra in its selected payment month. Every amount is capped at the remaining balance, so the schedule never produces a negative balance.
Worked Example with Two Extra-Payment Types
A $25,000 loan at 7% APR over 60 months has a scheduled payment of $495.03. The original schedule lasts 60 months, with $4,701.80 of interest and $29,701.80 total paid.
Add $100 recurring extra principal and a $1,000 one-time extra after payment 12. The accelerated schedule lasts 47 months, with $3,531.25 of interest, $28,531.25 total paid, and a final payment of $159.87.
Under these assumptions, the extra-payment schedule is 13 months shorter and has $1,170.55 less modeled interest. A lender may apply extra amounts differently, so confirm actual payment instructions and contract terms.
Annual Summary and Monthly Detail
The annual table reconciles accelerated principal, interest, payments, and remaining balance. The monthly detail preview shows the first 12 payments and the final payment when the loan lasts longer. This limits page size and keeps long schedules usable on mobile.
Total paid equals principal plus total interest within ordinary floating-point tolerance. Recurring and one-time extras are not added again after that reconciliation; doing so would double count principal.
Zero APR, One-Month Terms, and Large Extras
At zero APR, interest is zero and payments divide principal across the selected term. A one-month term includes exactly one monthly interest allocation when APR is positive. If an extra amount is larger than the balance remaining after the scheduled payment, only the exact remainder is applied.
A one-time extra scheduled after accelerated payoff is not applied. The calculator notes that state instead of counting a payment after the balance has reached zero.
Payoff Dates and Final Payments
An optional first-payment date produces original and accelerated payoff dates by adding whole calendar months. The day of month is capped when a later month is shorter. Dates do not include weekends, holidays, due-date changes, deferrals, or posting delays.
The final partial payment includes that month's interest and only the principal still due. It can be smaller than the scheduled payment, the scheduled-plus-extra amount, or both.
Not an Affordability or Qualification Tool
This page answers how an entered loan amortizes. It does not determine affordability, approval, collateral value, lender eligibility, credit-score effects, available rates, or whether refinancing is suitable.
For several existing debts under one monthly budget, use the Debt Snowball vs Avalanche Calculator. For one revolving card balance, use the Credit Card Payoff Calculator.
Common Mistakes and Limitations
Common mistakes include applying the annual rate directly each month, adding extra principal before interest when checking this schedule, counting extras twice, paying beyond zero, or assuming the last payment equals the regular payment. The model excludes fees, prepayment penalties, changing rates, daily interest, irregular frequencies, lender allocation rules, insurance, escrow, balloon payments, refinancing, mortgage rules, student-loan programs, taxes, qualification, and legal terms.
Frequently Asked Questions
Does extra principal always reduce interest?
It does in this simplified model because later interest uses a smaller balance. Actual contracts may apply payments differently or include fees or restrictions.
Why is the final payment smaller?
The calculator caps payment at the remaining principal plus that month's interest rather than overpaying and showing a negative balance.
What happens if the one-time extra is after payoff?
It is ignored because no balance remains. The result explains that it was not applied.
Are loan values included in URLs or analytics?
No. This calculator shares only its clean canonical page address. Inputs, outputs, and dates remain in the browser.