i What this calculator does
Works out the monthly instalment on a South African home loan from the amount, the interest rate and the term, and shows how much of what you repay is interest. Add an extra monthly payment and it re-runs the amortisation to show how many years and how much interest the extra saves, which is the number that matters most to anyone deciding between paying the bond down and investing.
The default rate is prime, which was 10.5% in the 2026/27 cycle; banks quote prime plus or minus a margin depending on your profile, so change it to the rate you were offered. The monthly service fee is added because it is part of what you actually pay, not of the interest calculation.
Illustrative only. Banks quote individual rates, may add fees not shown here, and your instalment changes when the prime rate moves. Not financial advice.
Frequently asked questions
How is a South African bond instalment calculated?
With the standard amortisation formula: instalment = loan × monthly rate ÷ (1 − (1 + monthly rate)^−months). The monthly rate is the annual rate divided by 12. Banks add a monthly service fee on top.
What rate do banks charge on home loans in 2026?
Prime, 10.5% in the 2026/27 cycle, plus or minus a margin based on your credit profile, deposit and the bank's appetite. Offers from prime minus 1% to prime plus 2% are common; the difference on a R1.5 million bond is several hundred rand a month.
Does paying extra into my bond really save that much?
Yes, because interest is charged on the outstanding balance every month, so every rand paid early stops earning interest for the bank for the rest of the term. On a 20-year bond, a modest extra payment made from the start typically cuts years off the term.
Should I pay extra into the bond or invest the money?
Paying into the bond is a guaranteed, tax-free return equal to your bond rate. Investing may return more but with risk and, outside a TFSA or retirement fund, tax. The Bond vs Invest Calculator on this site compares the two after tax.
What is an access bond?
A home loan facility that lets you withdraw extra payments you have made. It gives you the interest saving while the money is in the bond and liquidity if you need it back, which is why many South Africans use it as an emergency fund.
Why is my first instalment mostly interest?
Because interest is calculated on the full balance at the start. On a R1.5 million bond at 10.5% the first month's interest is R13,125; only the rest of the instalment reduces the capital. The split shifts toward capital as the balance falls.
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