Bond Calculator South Africa 2026
Calculate your monthly home loan repayment and total interest
Bond calculations are estimates based on current prime rate. Contact your bank for exact figures.
How a bond repayment is built
A South African home loan is almost always a monthly-repayment, variable-rate loan. The instalment has two components: interest on the outstanding balance, and the capital that reduces it. In the first year of a 20-year bond at 11,25%, roughly 93% of every payment is interest — which is why paying R500 a month extra early in the term is worth far more than the same R500 in year 15.
The formula the banks use
Monthly payment = P × [r(1+r)n] ÷ [(1+r)n − 1], where P is the loan amount, r is the annual rate ÷ 12 ÷ 100, and n is the term in months. Nothing else — no admin fee, no initiation fee — is inside that number, which is why your quoted instalment and the bank’s total cost of credit differ.
What R1 million costs at different rates and terms
| Rate | 20 years | 30 years | Extra interest over 30 years |
|---|---|---|---|
| 10,75% | R10 152,38 | R9 339,36 | R1 330 000 vs R1 219 000 |
| 11,25% | R10 492,56 | R9 712,61 | R1 496 000 vs R1 259 000 |
| 12,00% | R11 010,86 | R10 285,97 | R1 703 000 vs R1 338 000 |
A 1% rate difference on R1 million over 20 years is about R7 185 a year — R143 700 over the term. The term difference is bigger still: stretching from 20 to 30 years cuts the instalment by about R780 but adds roughly R280 000 of interest. That is the trade the calculator exists to make visible.
What the instalment does not include
- Transfer duty — nil below R1 210 000, then 3% and up (see the transfer duty calculator)
- Conveyancing fees — attorney fees plus SARS deed-office fees, typically R25 000–R45 000 on a R1 million purchase
- Bond registration costs — the bank’s attorney, usually R20 000–R30 000
- Initiation fee — capped by the National Credit Act, and it may be added to the loan
- Monthly bond insurance — homeowner’s cover is a condition of the loan, not part of the instalment
- Rates and levies — municipal, and often R1 500–R3 000 a month on top
Fixed versus variable
A fixed rate buys certainty for a period (usually two to five years) at a premium of roughly 0,5 to 1,5 percentage points over prime. It protects you if rates rise and costs you if they fall. On a R1 million bond a 1% premium is about R700 a month — decide whether the certainty is worth that, and remember the rate reverts to variable at the end of the fixed period.
How to pay it off years earlier
Three levers, in order of effect: pay extra into the capital every month (R1 000 extra on a R1 million 20-year bond at 11,25% cuts roughly four years and about R230 000 of interest); keep the instalment at its old level when the rate drops; and use a flexi or access facility to park surplus cash against the balance, where it reduces daily interest while remaining available.
Frequently Asked Questions About Home Loans
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How the bond calculator works
A bond instalment comes from the annuity formula: instalment = P × r ÷ (1 − (1 + r)^−n), where P is the loan, r the monthly interest rate (annual rate ÷ 12) and n the number of months.
A R1 000 000 bond at 11,25% over 20 years: r = 11,25% ÷ 12 = 0.009375, n = 240. The instalment is R10 492,56 a month, and the total repaid is R2 518 214 — R1 518 214 of which is interest.
Over 30 years the same bond costs R9 712,61 a month but R2 496 541 in interest — a lower instalment for a much larger total.
What changes the answer in South Africa
South African bonds are usually quoted at prime plus a margin, and prime moves with the Reserve Bank. The rate is linked, not fixed, unless you take a fixed-rate period. Extra payments go straight off capital only if you instruct the bank to reduce the term rather than the instalment, and that instruction is worth giving.
Common questions about the bond calculator
Does paying extra each month make a difference?
Yes, and disproportionately. An extra R1 000,00 a month on a R1 000 000 bond at 11,25% shortens the term by several years and saves a large multiple of the extra paid.
What is the difference between the instalment and the total cost?
The instalment is what you pay each month (R10 492,56); the total cost is instalment × months (R2 518 214), which includes R1 518 214 of interest.
Why is my bank's figure slightly different from a calculator?
Because of initiation fees, bond registration costs added to the loan, and the exact daily interest method the bank uses. Treat a calculator as close, not exact.