Loan Comparison Calculator

Compare two fully-amortising loans side-by-side. Type each loan's principal, annual rate, and term — see the monthly payment, total interest, total cost, and a verdict that names the cheaper option. A year-by-year balance chart shows how each loan amortises. Pure client-side math, no upload.

Loan A
Loan B
Verdict —
Monthly payment difference — A − B (per month)
Total interest difference — A − B (over the full term)
Total cost difference — A − B (over the full term)
Loan A — Monthly payment —
Total interest: — Total cost: — Effective APR: — Months: —
Loan B — Monthly payment —
Total interest: — Total cost: — Effective APR: — Months: —
Loan A balance Loan B balance

How it works

Each loan uses the standard amortising-loan formula: monthly payment equals P · r / (1 − (1 + r)−n), where r is the monthly rate (annual rate ÷ 12 ÷ 100) and n is the term in months. When the rate is zero the formula collapses to P / n.

Total interest equals the monthly payment times the number of payments, minus the principal. Effective annual rate is the nominal rate compounded monthly, expressed as a percentage. The verdict flags whichever loan has the lower total cost — a 30-year loan at 6% usually has a lower monthly payment than a 15-year loan at 5%, but it costs a lot more over its full term.

The year-by-year balance chart uses the closed-form balance(k) = P · (1+r)k − payment · (((1+r)k − 1) / r) to plot each loan's remaining principal after every whole year of payments.

Educational only — not financial advice. Real mortgages may include fees, taxes, insurance, escrow, and variable rates that this simple comparison does not model.