Loan Amortization Worked-Example Dataset — Monthly Payment, Interest/Principal Split, and Lifetime Interest

An open reference dataset for loan amortization math. The monthly payment on a fully-amortizing fixed-rate loan is computed with the standard formula P · r · (1+r)^n / ((1+r)^n − 1), where P is principal, r is the monthly interest rate, and n is the number of months. From that payment, each period splits into interest (balance × monthly rate) and principal (payment − interest), and the remaining balance declines month by month until it reaches zero. This dataset provides six worked scenarios — an auto loan, a personal loan, and 15- and 30-year mortgages — with the monthly payment, total paid, total interest, and interest as a percentage of principal, plus a per-period breakdown for a representative mortgage showing how the interest/principal split shifts over the life of the loan. The same algorithm is published as the open-source amortization-schedule crate (pure Rust, no dependencies) and is live as the Asset Loan Calculator, an amortization-schedule tool. Columns: scenario, principal_usd, annual_interest_rate, term_months, monthly_payment_usd, total_paid_usd, total_interest_usd, interest_pct_of_principal. A second block lists period_month, interest_usd, principal_usd, remaining_balance_usd. License: CC0 / public domain.