Interest Rate Change Calculator
See how much your bond or loan repayment changes when interest rates move up or down.
Your loan and the rate change
Worked example
These are the calculator's starting values, so the results above match this example until you change an input.
On a R 1 500 000 bond at 10.5% with 240 months left, the repayment is R 14 975,70. A 0.25 percentage point rate rise takes it to R 15 228,43.
That is +R 252,74 a month, or +R 60 656,64 over the remaining term if the rate stays at the new level.
How rate changes reach your bond
The South African Reserve Bank’s Monetary Policy Committee meets six times a year and sets the repo rate. Banks set their prime lending rate 3.5 percentage points above repo, and most home loans and many car and personal loans are priced at prime plus or minus a margin. When repo moves by 0.25 percentage points, a variable-rate loan usually moves by the same amount from the next month.
| Rate change | On a R 1 500 000 bond at 10.5% over 20 years |
|---|---|
| +0.50 points | About R 507 more a month |
| +0.25 points | About R 253 more a month |
| −0.25 points | About R 251 less a month |
| −0.50 points | About R 500 less a month |
What you can do when rates fall
Many banks lower your instalment automatically when rates fall. If you can afford it, keep paying the old amount: the difference goes straight to the capital and can take years off the bond. Use the bond extra payment calculator to see the effect.
How this calculator works
It works out the standard monthly repayment on the outstanding balance over the months left, at today’s rate and at the new rate, assuming the term stays the same. Some banks keep the instalment and change the term instead. Fixed-rate loans do not change until the fixed period ends.
Based on standard amortising loan maths with interest charged monthly. Prime is set by banks at repo plus 3.5 percentage points; see the South African Reserve Bank for the current repo rate and MPC dates. This page is general educational information, not financial advice.
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Open calculator →Frequently asked questions
How much does a 0.25% rate cut save on my bond?
On a R 1.5 million bond at 10.5% with 20 years left, about R 251 a month. Enter your own balance and term to see your figure.
How often does the repo rate change?
The Monetary Policy Committee meets six times a year and can raise, cut or hold the rate at each meeting.
What is the prime rate?
The rate banks use as the base for most loans. In South Africa it is set at the repo rate plus 3.5 percentage points.
Related guides
How home loans work
A home loan, or bond, pays for most of a property and is repaid in equal monthly instalments over a set term, usually 20 years.
Read guide →GUIDEWhat affects loan repayments?
Four things set a loan repayment: how much you borrow, the interest rate, the number of months, and fees.
Read guide →