Interest Rate Change Calculator
See how SARB rate changes affect your monthly bond payment and total interest
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Understanding Interest Rate Changes SARB • Prime rate • Impact
How SARB Rate Changes Affect Your Bond
The South African Reserve Bank (SARB) Monetary Policy Committee (MPC) meets roughly every two months to review the repo rate — currently 6.75%. Commercial banks set their prime lending rate at repo + 3.5%, currently 10.25%.
Most South African home loans are variable-rate, linked to prime. When the SARB cuts the repo rate by 25 basis points (0.25%), banks typically pass this on in full, reducing prime and your bond rate by the same amount. Your new monthly instalment is recalculated from the following month.
The Impact Formula
Where PMT uses the standard annuity formula with monthly compounding. The key insight: on a variable-rate bond, the outstanding balance and remaining term at the time of the rate change determine the new payment — not the original loan amount.
Worked Example
Lerato has an outstanding balance of R980,000 with 15 years remaining at 10.25%. The SARB cuts rates by 50bp (0.5%).
Old payment: R10,840/month
New payment at 9.75%: R10,476/month
Monthly saving: R364/month | Annual saving: R4,368/year
Over the remaining 15 years, the lower rate saves approximately R65,500 in total interest.
If Lerato keeps paying R10,840/month (the original amount) despite the lower rate, she would pay off her bond 14 months earlier and save an additional R18,000.
Historical SARB Rate Cycles
The SARB has gone through several rate cycles since 2015. Prime peaked at 10.5% in 2016, dropped to a historic low of 7.0% in 2020 during COVID-19 emergency cuts, then climbed back to 11.75% by mid-2023 as inflation surged. As of early 2025, prime sits at 10.25% after a series of 25bp cuts from late 2024.
Understanding this cycle helps homeowners plan: locking in higher extra payments during low-rate periods provides a significant buffer when rates rise again.
Frequently Asked Questions
How often does the SARB change interest rates in South Africa?
The SARB Monetary Policy Committee (MPC) meets six times per year, roughly every two months. Each meeting can result in a rate increase, decrease, or hold. Emergency meetings outside this schedule are rare but have occurred (e.g., the COVID-19 emergency cuts in 2020).
Rate changes are typically announced on a Thursday and take effect from the following day. Banks usually adjust variable-rate bond instalments from the next billing cycle.
How much does a 1% interest rate increase cost on my bond?
On a R1,000,000 outstanding balance with 15 years remaining, a 1% rate increase costs approximately R680/month extra. Over the remaining term, this equates to roughly R122,000 in additional interest.
As a rule of thumb for South African bonds: each 0.25% rate change costs or saves approximately R170/month per R1,000,000 of outstanding balance with 15 years remaining.
Should I fix my bond rate when interest rates are expected to rise?
Fixed-rate home loans are relatively uncommon in South Africa. When offered, they typically come at a premium of 1–2% above the current variable rate to account for the bank's risk of rates falling. In South Africa's history, fixed rates have generally cost more than staying variable.
A better strategy for most South African homeowners is to build a payment buffer: when rates are low, continue paying the higher amount. This builds equity faster and protects you when rates rise again. Use the Fixed vs Variable Calculator to compare the two strategies for your specific situation.
What is a basis point and how is it used in rate discussions?
A basis point (bp) is one-hundredth of a percentage point (0.01%). Rate changes are commonly described in basis points to avoid ambiguity:
- 25bp = 0.25% (a quarter-point move — the most common SARB increment)
- 50bp = 0.5% (a half-point move)
- 100bp = 1.0% (a full-point move — uncommon)
The SARB has historically moved in 25bp or 50bp increments. Emergency 100bp cuts occurred twice during the 2020 COVID-19 crisis.
Will my bank automatically reduce my monthly payment when rates drop?
Yes — most South African banks automatically recalculate your instalment when the prime rate changes. You will typically receive an SMS or email notification of your new instalment amount.
However, you can opt to keep paying the higher amount. The extra portion goes directly toward principal reduction, accelerating your payoff date. This is often the best use of a rate-cut windfall for homeowners with a variable-rate bond.