How is a South Africa bond repayment calculated?

The standard amortising loan formula is used: M = P·r·(1+r)^n / ((1+r)^n − 1), where P is the loan amount, r is the monthly rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12). This is the same maths every SA bank applies to a home loan.

What rate should I use?

Most South African home loans are variable and quoted relative to the prime lending rate, which has been around 11.75%. A strong applicant may secure prime or below; others pay prime plus a margin. Use the rate your bank quotes, and check the stress-test figure for room if prime rises.

Banks often lend up to 100% LTV for qualifying buyers, but a deposit of 10% to 20% lowers your loan, monthly payment and total interest, and usually earns a better rate. First-time-buyer 100% bonds exist but cost more over the term.

Why does the tool show a stress test?

South African bond rates are variable, so a rate increase raises your payment immediately. The stress test recomputes the repayment at a rate two percentage points higher so you can check you could still afford the bond if prime climbs.

Does this include other ownership costs?

No. The repayment covers principal and interest only. Budget separately for transfer duty and bond registration costs at purchase, plus ongoing rates, levies (for sectional title), insurance and maintenance.

South Africa Mortgage Calculator

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A South African home loan — a “bond” — is a standard amortising loan, but its rate is usually variable and linked to the prime lending rate. This calculator produces your monthly repayment, total interest over the term, and a stress test at a higher rate so you can judge affordability the way a bank does.

How it works

The monthly repayment uses the amortising-loan formula:

P = price − deposit            (loan amount)
r = annualRate / 100 / 12      (monthly rate)
n = years × 12                 (number of payments)
M = P · r · (1 + r)^n / ((1 + r)^n − 1)

If the rate is 0, the payment is simply P / n. Total interest is M · n − P. The stress test repeats the calculation at annualRate + 2% to show how a prime increase would affect you.

Example and tips

A 1,500,000 ZAR property with a 150,000 deposit gives a 1,350,000 loan. At 11.75% over 20 years (240 payments) the monthly repayment is about 14,629 ZAR, with total interest near 2.16 million over the life of the bond. Because the rate is variable, always check the stress-test figure: at 13.75% the same bond costs roughly 16,442 a month. A larger deposit cuts both the payment and the total interest substantially.