Extra bond payment calculator: how much is your bond overcharging you? (South Africa, 2026)
Paying extra works hardest when your rate is above prime. On a R 1 500 000 bond with 20 years left at 11.75% (prime + 1.0pp), an extra R 1 000 a month saves about R 527 838 in interest and settles the bond about 3.7 years sooner — assuming the rate stays constant and your bank applies the extra to the balance each month.
How much could paying extra save you?
These numbers are illustrative estimates, not an offer and not guaranteed savings. Your actual rate, recalculation and prepayment terms depend on your bank's assessment and its fee schedule.
Last updated: 2026-09-23. Prime is shown as 10.75%. Your actual rate depends on your credit profile, deposit and the bank’s assessment. Figures are illustrative estimates, not a quote or a guarantee of savings.
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What each extra amount saves you
At your current balance, rate and remaining term, this is what each standard extra-per-month amount would do — estimates with the same assumptions as the calculator above.
| Extra per month | Term shortened by | Interest saved |
|---|---|---|
| R 500 | 1 year 11 months | R 257 259 |
| R 1 000 | 3 years 6 months | R 451 519 |
| R 2 000 | 5 years 10 months | R 730 201 |
The short answer
- R 500 extra a month on a R 1 500 000 bond at 11.75% with 20 years left: saves about R 303 806 in interest and pays the bond off about 2.1 years sooner.
- R 1 000 extra a month on a R 1 500 000 bond at 11.75% with 20 years left: saves about R 527 838 in interest and pays the bond off about 3.7 years sooner.
- R 2 000 extra a month on a R 1 500 000 bond at 11.75% with 20 years left: saves about R 842 927 in interest and pays the bond off about 6.0 years sooner.
- The rate itself is the bigger lever. At prime +1.0pp instead of prime, the same R 1 500 000 bond costs R 1 027 more per month — about R 246 521 over the term — before any extra payments.
- Fix the rate first, then feed the bond. Switching to an illustrative 10.25% saves about R 367 429 in interest against once-off costs near R 45 306; switch and pay R 1 000 extra, and the combined saving on the example is about R 783 655.
How much does a rate above prime cost you?
A bond is “overcharging” you when your rate sits above the rate another bank would offer on the same profile — the banks price each applicant on credit record, deposit and loan-to-value, so two borrowers with the same balance can pay very different rates. That gap is measured in rands, and it compounds every month on your full outstanding balance, which is why it usually dwarfs what an extra payment alone can recover.
| Outstanding balance | Monthly at 10.75% (prime) | Monthly at 11.75% (prime + 1.0pp) | Overcharge per month | Overcharge over 20 years |
|---|---|---|---|---|
| R 1 000 000 | R 10 152 | R 10 837 | R 685 | R 164 347 |
| R 1 500 000 | R 15 228 | R 16 256 | R 1 027 | R 246 521 |
| R 2 000 000 | R 20 305 | R 21 674 | R 1 370 | R 328 695 |
Illustrative examples at a 20-year remaining term, nominal annual rates compounded monthly, computed at the prime lending rate of 10.75% (prime of 10.75% (effective 2026-09-25, verified 2026-09-23, source: South African Reserve Bank (SARB))). The 11.75% column is an illustration of a above-prime pricing, not a claim about any bank’s rates; offers across the major banks typically land between prime minus 1.0% and prime plus 2.0% depending on profile.
Your number depends on two things: your outstanding balance, and how far above prime your rate sits. Enter both in the calculator above — the rate is on your bond statement or your bank’s app, next to prime — and the estimate updates instantly. Seeing what a lower rate would save you first? Check whether switching breaks even for you, then come back and run the extra-payment numbers on the better rate.
Should you pay extra, or switch to a lower rate first?
A lower rate cuts the interest charged on every remaining rand for the rest of the term, while an extra payment only removes the rands you actually pay in — so if your rate is above what the market would offer you today, repricing or switching usually saves more than the same money paid into the bond. Extra payments still have one advantage nothing else matches: they need no application, no costs and no one’s approval, so they start working this month.
| Scenario | Once-off cost | Monthly change | Interest saved |
|---|---|---|---|
| Pay R 1 000 extra a month, keep your rate (term shortens by about 3.7 years) | R 0 | +R 1 000 | R 527 838 |
| Switch to 10.25%, term unchanged (break-even in about 30 months) | R 45 306 | −R 1 531 | R 367 429 |
| Switch, and pay R 1 000 extra a month | R 45 306 | −R 531 | R 783 655 |
Interest saved is measured over the remaining term against today’s bond at 11.75%, assuming rates stay constant and switching costs are paid in cash. Switching costs are composed from the published conveyancing, Deeds Office and initiation-fee scales (see the bond and transfer cost calculator) and exclude any early-settlement or cancellation penalty your current bank may charge. Not financial advice — an estimate to compare options, and your bank decides both rates.
This is not an argument against extra payments — it is an ordering. Reprice the bond first, then every extra rand works on a cheaper balance: in the worked example, the same R 1 000 a month saves about R 783 655 combined versus R 527 838 on its own. And never pay extra into an expensive bond while you carry dearer debt elsewhere — the credit card at 20%-plus outranks the bond at any prime-linked rate. ooba reports an average concession of about 0.67% below prime across the bonds it registers (checked 2026-10-03): evidence that the rate gap is worth chasing, because banks competing for the same deal do move their offers.
How the extra-payment calculation works
The calculator models the standard reducing-balance convention South African banks use for home loans: interest accrues monthly on the outstanding balance, your instalment settles that interest first, and the remainder reduces the principal. A once-off lump sum is credited against your balance in the first month, so every month after that charges interest on a smaller balance.
In shorten-the-term mode your instalment stays at its current level plus the extra amount, so the balance reaches zero sooner. In reduce-the-instalment mode you keep paying the extra, and after each month’s payments the bank recalculates your instalment on the reduced balance over the original remaining term — so your committed payment comes down while the term stays the same. The payoff is simulated month by month — including the final, smaller instalment — so the estimate is correct to the cent at the stated rate.
The rate is prefilled from the current prime lending rate of 10.75%, but move it to the rate on your statement — that number, not prime, is what your bond actually charges.
Assumptions and methodology:
- Nominal annual interest rate compounded monthly (monthly rests), reducing balance — the standard South African home-loan convention.
- Monthly rate factor i = annual rate % ÷ 100 ÷ 12 (e.g. 10.75% → 0.008958 per month).
- Fixed annuity instalment: payment = P × i ÷ (1 − (1 + i)^−n), where P is the outstanding balance and n the remaining months.
- An extra payment reduces the principal in the same month it is made, immediately after the scheduled instalment. Interest the following month is charged on the reduced balance.
- In reduce-term mode the schedule ends when the balance reaches zero; the final payment is a smaller residual amount.
- In reduce-payment mode the instalment is recalculated after each extra payment over the remaining term at the unchanged rate. This models ideal bank behaviour — actual banks may only recalculate on request or at the annual rest date, so a real reduced instalment can lag the calculator.
- The calculation assumes the variable interest rate stays constant for the whole remaining term. Any future rate change alters both the scheduled instalment and the effect of extra payments.
- Keep full floating-point precision internally; round to the nearest rand only at display. Never round month-by-month balances or interest — that is how schedules drift off by rand amounts.
Rate basis: Current prime + 0.00pp margin (illustration assumes you are charged exactly prime). Prime is 10.75% (effective 2026-09-25, verified 2026-09-23 against South African Reserve Bank (SARB)). Actual bank rates differ per applicant and per bank.
What this estimate leaves out: bond initiation and monthly service fees, homeowner’s insurance and credit life, rates and levies, any early- settlement or recalculation fees your bank charges, and the effect of future interest-rate changes. Banks decide rates and applications — this is an estimate, not an offer of finance.
These figures are illustrative, not a quote or an offer of finance. The pre-filled rate is the current prime lending rate of 10.75% as at 2026-09-23 (source: South African Reserve Bank (SARB)), and assumes you are charged exactly prime. Your actual rate depends on your credit profile, deposit and the bank’s assessment, and may be above or below prime — it differs for every applicant. The calculation assumes the interest rate stays constant for the whole remaining term, that every extra payment is applied to your bond in full in the month you make it, and that no fees or charges apply. Banks recalculate reduced instalments in their own way and on their own timing, so a real result can differ from this illustration. This calculator shows what could happen to a bond under these assumptions. It does not guarantee any saving, term reduction, reduced instalment or loan approval. Confirm the actual effect of an extra payment with your bank before relying on it.
Last updated: 2026-10-09.
Common questions about extra bond payments
Is it worth paying extra into my bond?
Paying extra reduces the balance your interest rate is charged on, so it cuts both the term and the total interest you pay — and unlike almost any other investment decision, the "return" is your bond rate, earned without risk. At the illustrative rate of 11.75% on a R 1 500 000 bond with 20 years left, an extra R 1 000 a month saves about R 527 838 in interest. Whether it beats your other options depends on your situation — expensive debt first, then emergency savings, then your bond. The calculator above shows the estimate for your actual balance, rate and term.
How much interest am I overpaying if my rate is above prime?
The gap between your rate and the best rate you could qualify for is the real cost of an uncompetitive bond — banks price per applicant, so paying above prime is not a fee, but it is money you may not have to pay. Every 1% above prime on a R 1 500 000 bond with 20 years left adds about R 1 027 a month — roughly R 246 521 over the term. Check your statement rate against today's prime, then ask your bank to reprice or have an originator submit your bond to several banks at once: ooba reports an average concession of about 0.67% below prime across the bonds it registers (checked 2026-10-03).
Should I pay extra into my bond or switch to a lower rate first?
For most borrowers the rate comes first, because a lower rate cuts the interest on every remaining rand for the rest of the term, while an extra payment only works on the rands you pay in. On the worked example, switching from 11.75% to an illustrative 10.25% saves about R 367 429 in interest against once-off costs near R 45 306 — break-even in about 30 months. But extra payments need no permission, no costs and no application, so you can start this month while you shop your rate. Do both and the effects stack: about R 783 655 saved in total on the example. Estimates only — your numbers depend on your balance, rate and the offers you actually get.
Should I reduce my term or my monthly instalment?
When you pay extra, most South African banks let you choose. Keeping your instalment the same and shortening the term saves the most interest, because you keep paying the higher amount. Asking the bank to recalculate your instalment down lowers your monthly commitment and frees cash flow, but saves less interest over the remaining term. You can switch between the two modes in the calculator to compare the estimates.
Can I get my extra payments back if I need the money?
Only if your bond has an access facility (sometimes called an access bond) that lets you withdraw prepaid amounts, and only up to the limit your bank sets. Not every bond or bank offers this, and terms differ — read our guide to access bonds in South Africa before relying on it as an emergency fund.
Does my bank charge a fee for paying extra into my bond?
Banks handle this differently. Some charge a small administration fee when they recalculate your instalment or issue an early-settlement quote, and minimum prepayment amounts can apply. Ask your bank about its prepayment, recalculation and early-settlement fees before you pay in a large lump sum.
Related tools and guides
- Suspect your rate is the problem? Read how bond switching works in South Africa — what it costs, what it saves, and when it breaks even.
- Want the break-even maths before you commit? Work out whether refinancing is worth the switching costs with the break-even guide and calculator.
- Starting a new bond rather than paying extra on an existing one? Work out the monthly repayment with our bond calculator.
- Want the mechanics behind extra payments? Read our guide to paying extra into your bond — how the bank recalculates, which option to ask for, and the fees to check.
- Hoping to withdraw the extra again later? Understand how an access bond works in South Africa.
- Considering settling the bond in full instead? Read our guide to paying off your bond early — settlement quotes, early-termination fees, and the NCA rules that protect you.
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