Loan Repayment Calculator
Monthly payment, total interest, and the year-by-year balance — updates as you type.
Year-by-year amortization
| Year | Interest paid | Capital paid | Balance |
|---|
How this is calculated
Fixed-rate loans amortize: every payment is identical, but its interest/capital split shifts over the term. The monthly payment comes from the standard amortization formula:
M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) where r = annual rate ÷ 12, n = years × 12
Worked example: borrowing R250,000 at 11.25% over 20 years gives r = 0.009375 and n = 240, so M ≈ R2,623 per month — about R629,500 paid in total, of which roughly R379,500 is interest. That last number is why the term slider matters more than any other: the same loan over 10 years costs about R168,000 in interest — less than half — for a higher monthly payment.
Reading the result like a lender does
Lenders typically want repayments under about a third of gross income; multiply the monthly result by three for a rough affordability line. And because interest accrues on the outstanding balance, any extra capital paid in the first few years removes whole payments from the end of the schedule — the table above shows how slowly the balance falls early on, which is exactly why early overpayments are so effective.
Frequently asked questions
How is the monthly repayment calculated?
With the standard amortization formula M = P·r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the amount borrowed, r the monthly interest rate (annual rate ÷ 12), and n the number of monthly payments. It is the same formula banks use for fixed-rate loans, and this page computes it live in your browser.
Does this work for a home loan or bond?
Yes — a mortgage or bond is an amortized loan, so the math is identical: enter the amount after your deposit, the interest rate, and the term. For house-specific extras like deposit percentage sliders, use the dedicated bond repayment calculator.
Why is so much of my early payment interest?
Interest is charged on the outstanding balance, which is biggest at the start. Early payments are therefore mostly interest; as the balance falls, more of each identical payment goes to capital. The year-by-year table below the result shows exactly how that flips over the term.
How can I pay less interest in total?
Three levers: a shorter term (the biggest one — compare 20 vs 30 years in the calculator), a lower rate (even 0.5% matters over decades), and paying extra toward capital early, when the balance is largest. Small early overpayments remove entire payments from the end of the loan.
Is anything I type sent to a server?
No. The calculation runs entirely in your browser — amounts, rates, and terms never leave your device. You can load this page, disconnect from the internet, and it still works.