HubTools

Loan Calculator

Loan calculator with biweekly mode, extra monthly payments, one-time lump sums, full amortization, and CSV export. 100% client-side.

How is Loan Amortization Calculated?

Loan amortization is the process of splitting each fixed monthly payment into an interest portion (calculated on the remaining balance at the monthly rate, annual rate ÷ 12) and a principal portion (whatever is left of the payment), using the standard PMT formula P × [r(1+r)n] / [(1+r)n− 1] to set the payment so the balance reaches zero in exactly n months. Because interest is charged on the outstanding balance, early payments are mostly interest and later payments are mostly principal — on a 30-year loan at 7%, you don't cross the 50% principal mark until roughly year 20. This calculator models recurring extra payments, one-time lump sums, and biweekly cadence (which silently turns 12 monthly payments into 13 over a year), then exports the whole schedule as CSV. Buying a home? Use the Mortgage Calculator. Tackling multiple debts? Try the Debt Calculator.
Loan Details
Loan Amount
Annual Interest Rate
%
Loan Term
60 months (5 years)
Payment Frequency
Results
Monthly Payment
$188.71
Total Interest
$1,322.74
Total Paid
$11,322.74
Amortization Schedule
MonthPaymentPrincipalInterestBalance
1$188.71$147.05$41.67$9,852.95
2$188.71$147.66$41.05$9,705.30
3$188.71$148.27$40.44$9,557.02
4$188.71$148.89$39.82$9,408.13
5$188.71$149.51$39.20$9,258.62
6$188.71$150.13$38.58$9,108.48
7$188.71$150.76$37.95$8,957.72
8$188.71$151.39$37.32$8,806.34
9$188.71$152.02$36.69$8,654.32
10$188.71$152.65$36.06$8,501.66
11$188.71$153.29$35.42$8,348.37
12$188.71$153.93$34.78$8,194.45

How to use this tool

  1. 1
    Enter loan terms
    Input the loan amount (principal), annual interest rate, and term. Works for auto, personal, student, and any fixed-rate installment loan.
  2. 2
    Pick a payment frequency
    Choose Monthly or Biweekly. Biweekly produces 26 half-payments per year, equivalent to 13 monthly payments — automatically shortens the loan by several months.
  3. 3
    Add extra payments (optional)
    Open the Extra Payments panel. Enter a recurring monthly extra, or add one-time lump sums at specific months (e.g. 'apply $5,000 at month 24').
  4. 4
    Read the comparison alert
    When extras are active, a green alert shows exactly how many months you saved and how much interest you avoided versus the no-extras baseline.
  5. 5
    Inspect or export the schedule
    Review the month-by-month breakdown of interest, principal, and remaining balance. Click CSV to download the complete schedule for spreadsheet analysis.

Frequently asked questions

How is my monthly loan payment calculated?
We use the standard amortization (PMT) formula: P × [r(1+r)^n] / [(1+r)^n − 1], where P is the principal, r is the monthly interest rate (annual rate ÷ 12), and n is the number of months. Each payment goes partly to interest, partly to principal, with the principal share growing over time.

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