How much does a 1 percent rate increase cost on your bond?
See the exact monthly and lifetime cost of a 1% rate hike on your home loan — in under 10 seconds. No signup needed.
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These numbers are illustrative estimates, not an offer. Your actual rate and repayment depend on your credit profile, deposit and each bank's assessment.
Last updated: 2026-09-12. Prime is shown as 10.5%. Your actual rate depends on your credit profile, deposit and the bank’s assessment.
At 10.50% your repayment is R 14 976. If the rate rises by 1%, your repayment becomes R 15 996. That’s an extra R 1 021 per month — R 244 979 more over the full term.
Estimate only — assumes a fixed rate for the remaining term, monthly repayments in arrears, no fees or insurance. Not a quote or pre-approval.
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Why 1% matters more than it sounds
One percentage point does not sound dramatic — until you convert it into rands over a 20-year bond. On a R1 million home loan at the current prime rate of 10.50%, a 1% increase raises the monthly repayment from R 9 984 to R 10 664. That is R 680 more every single month, and roughly R 163 319 more over the remaining term — money that buys nothing extra except time.
The same maths works in your favour when rates fall: a 1% cut frees up roughly the same amount each month (the repayment curve is not perfectly symmetric, so toggle the scenario above for the exact figure). Either way, the lesson is the same: the interest rate is the biggest lever on what a bond costs you, which is why the rate you are offered deserves as much attention as the purchase price.
| Bond amount | Monthly at 10.50% | Monthly at 11.50% | Extra per month | Extra over 20 years |
|---|---|---|---|---|
| R 1 000 000 | R 9 984 | R 10 664 | R 680 | R 163 319 |
| R 1 500 000 | R 14 976 | R 15 996 | R 1 021 | R 244 979 |
| R 2 000 000 | R 19 968 | R 21 329 | R 1 361 | R 326 639 |
Illustrative examples at a 20-year term, no margin above or below prime, rates as of 2026-09-12. Your actual rate may be prime plus or minus a margin set by the bank.
How the calculator works
Enter your outstanding bond amount, the term remaining and your current interest rate. The calculator applies the standard annuity (reducing-balance) formula South African banks use — each month you pay interest on the outstanding balance and the remainder reduces the principal — at your current rate and at 1 percentage point higher or lower, then shows the difference in rands per month and over the full term.
The rate slider starts at the current prime lending rate of 10.50%, but move it to match the rate on your statement — most South Africans pay prime plus or minus a margin. For the repayment on a new purchase (deposit included), use the bond repayment calculator.
Assumptions: monthly repayments in arrears; a fixed rate for the remaining term; no bond-registration, transfer, attorney, insurance or other costs; the rate is an annual nominal rate compounded monthly. Rand values are rounded to the nearest rand for display only — calculations keep full precision.
Last updated: 2026-09-12.
Why rates change
South African home-loan rates are priced off prime, and prime moves with the repo rate set by the South African Reserve Bank at its Monetary Policy Committee meetings. When the MPC raises the repo rate to keep inflation inside its target band, banks pass the increase on by raising prime — and every variable-rate bond repayment in the country is repriced upward within weeks.
That pass-through is mechanical, not discretionary: prime is conventionally repo plus 3.50 percentage points. It is why the cost of a rate cycle is knowable in advance, down to the rand — and why stress-testing your own bond against a 1% move before the MPC meets is worth two minutes of your time.
What to do next
- Buying soon and want your baseline repayment? Calculate your current bond repayment.
- Working out what price range still works if rates rise? Use our home loan affordability calculator.
- Budgeting the full picture of buying costs? Read about upfront bond registration and transfer costs.
- Want a human to sense-check your numbers? Talk to a registered bond consultant.
This calculator is for illustration only and does not constitute financial advice. The rate you are offered depends on your credit profile, deposit, and the bank's assessment. Rates are current as of 2026-09-12.
Common questions about rate increases and bonds
How much does a 1% rate increase cost on a R1 million bond?
On a R1 000 000 bond over 20 years at the current prime rate of 10.50%, a 1% increase adds roughly R 680 a month — about R 163 319 more over the full term. Use the calculator above to see the number for your exact bond amount, rate and remaining term.
Why does a 1% interest rate increase change my bond repayment?
A South African home loan is repaid on a reducing balance: each month you pay interest on what you still owe, and the rest of the instalment pays down the principal. When the interest rate rises, the interest portion of each instalment grows, so the instalment itself is recalculated upward to clear the same loan over the same term. That is why even a "small" 1% move is worth real money every month for years.
How is the bond repayment impact of a rate increase calculated?
With the standard annuity formula South African banks use: M = P × [i(1+i)ⁿ] / [(1+i)ⁿ − 1], where P is the outstanding loan amount, i is the annual rate divided by 12, and n is the remaining term in months. The calculator applies that formula at your current rate and at 1 percentage point higher (or lower), and shows the difference in rands. Bond registration, transfer, attorney and insurance costs are excluded.
Will my bond repayment go up automatically if the prime rate increases?
If your rate is linked to prime — as most South African home loans are — then yes. When the South African Reserve Bank moves the repo rate, banks adjust their prime rate, and your instalment is repriced at the next adjustment date in your loan agreement. If you fixed your rate, your repayment stays unchanged until the fixed period ends, at which point it resets to whatever the variable rate is then.
What can I do to reduce the impact of a rate increase on my bond?
Paying extra into your bond reduces the principal the next month’s interest is calculated on, so it softens every future rate rise and shortens the term. Building a repayment buffer before hikes land, and making sure your rate is competitive in the first place — banks price the same profile differently, which is why comparing offers matters — both reduce what a hiking cycle costs you. Extending the term lowers the instalment but increases total interest.
How much does a 0.25% rate hike cost on my bond?
A 25 basis point move costs about a quarter of a 1% move. On a R1 000 000 bond over 20 years at the current prime rate of 10.50%, a 0.25% increase works out to roughly R 168 more per month — R 40 438 over the full term. You can test any scenario with the sliders above.
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