Use this when you need a fixed-rate loan or mortgage's level monthly payment plus a year-by-year amortization schedule (principal paid, interest paid, remaining balance) rather than doing the amortization arithmetic yourself.

Use this when you need a fixed-rate loan or mortgage's level monthly payment plus a year-by-year amortization schedule (principal paid, interest paid, remaining balance) rather than doing the amortization arithmetic yourself. Uses the standard payment formula and handles the 0% case (payment = principal / months, all principal). annualRate is a percent (6.5 = 6.5%); years is 1-50. Deterministic: same input, same output. Example: principal 300000, annualRate 6.5, years 30 -> monthlyPayment 1896.20, totalInterest 382633.47, numberOfPayments 360, and a 30-row schedule (one per year).