Calculate monthly payments, total interest, and generate amortization schedules for loans and mortgages.
Type the total amount you plan to borrow.
Enter the annual interest rate for the loan.
Set the repayment period in months or years.
See monthly payments, total interest, and amortization schedule.
A loan balance becomes a payoff plan once you enter the amount borrowed, annual interest rate, and term. The calculator derives the level monthly principal-and-interest payment, totals all scheduled interest, and lays out the balance after each installment. It is intended for a rate that stays unchanged throughout the term. The common surprise is that the calculated payment is not necessarily the full cost of owning a home: property tax, insurance, association dues, points, and lender fees are separate unless explicitly represented by the available inputs.
A concrete input and expected output from the current implementation.
Input
Loan amount: $1,200 Annual interest rate: 12% Loan term: 1 year
Expected output
Monthly payment: approximately $106.62 Total of payments: approximately $1,279.42 Total interest: approximately $79.42 Amortization schedule: 12 monthly payments
The monthly rate is 1%, and the level-payment formula gives an unrounded payment of about $106.618546. Twelve unrounded payments total about $1,279.42, so the interest above the $1,200 principal is about $79.42.
The annual rate is divided by 12 to obtain the monthly rate r, and the term is converted to n monthly installments. For principal P and a nonzero rate, the scheduled payment is P * r * (1 + r)^n / ((1 + r)^n - 1). At zero interest, the payment is simply P / n.
For each schedule row, monthly interest equals the opening balance times r. The rest of that month's payment reduces principal, producing the next balance. Because the opening balance usually shrinks, the interest share falls while the principal share rises. Total interest is the sum of the row interest amounts; the final installment can differ slightly after cent rounding.
Interest for each installment is based on the balance before that payment. Early in a long mortgage, that balance is near the original principal, so more of the fixed payment goes to interest. As principal declines, the interest charge declines and more of the same payment reaches principal. This is normal for level-payment amortization, not an added penalty.
Not always. It should be close for a fixed-rate monthly loan when the amount, note rate, term, payment timing, and rounding conventions agree. It will not reproduce fees, points, escrow costs, adjustable-rate changes, daily-interest conventions, or an irregular first payment unless those differences are represented. Use the lender's disclosures for contractual figures.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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