What will it repay a month?
One figure in, two out. The monthly instalment, and what the loan costs you in the end.
About the loan
What you are borrowing, and over how long.
Nothing you type here is saved, submitted, or seen by a credit bureau. The sums happen in this browser.
A guide, not an offer. Every lender does its own affordability assessment under section 81 of the National Credit Act, off your bank statements and your credit record, and that is the only one that counts. The rates above are prime (10,75% from 25 September 2026) plus a rough published margin for each kind of finance, because the rate you are granted depends on a credit record we have not seen.
The instalment is the easy half. The figure that decides whether a longer term was a good idea is the total interest, and almost nobody puts it on the screen beside the monthly number — because over twenty years it is frequently larger than the house.
The term is the biggest lever, and it cuts both ways
Stretching a loan over more years makes the monthly figure smaller, which is why it is the first thing offered to somebody who says the instalment is too high. It also means paying interest for longer on a balance that comes down more slowly, and the total can move by a great deal more than the monthly saving suggests. Work both out before you agree to a longer term, not afterwards.
A small difference in rate is not a small difference in money
Half a per cent sounds like rounding. Over the life of a bond it is not, and it is the single thing an originator can move for you: the same application at several banks comes back at several rates, and the gap between the best and the worst is usually worth far more than anything else in the transaction.
Paying in extra
Anything paid above the instalment comes off the capital, so it stops earning the bank interest for the rest of the term. That is why a modest regular overpayment early on takes years off a bond, and why the same money paid in near the end barely moves it. Ask your lender how to make an extra payment reduce the TERM rather than the instalment — on most bonds it is a choice, and the default is usually the one that suits them.
Questions
How is a bond repayment calculated?
It is the standard amortisation formula: the instalment is the amount borrowed multiplied by the monthly rate, divided by one less (1 + the monthly rate) to the power of minus the number of months. In plain words, it is the level monthly figure that clears the loan and the interest on it exactly, over the term. Early instalments are mostly interest and late ones are mostly capital, which is why overpaying early does so much more than overpaying late.
Does a longer term mean a cheaper bond?
A cheaper month and a dearer bond. The instalment falls because the same capital is spread over more payments, and the total rises because interest is charged for longer on a balance that comes down more slowly. The calculator above shows both figures together for exactly this reason.
What rate will I actually get?
Not one anybody can tell you from a calculator. A lender prices off your credit record, your deposit and how much of the purchase it is being asked to fund, and two banks looking at the same application routinely come back at different rates. That gap is the thing worth shopping for, and it is what putting one application to several banks is for.
Read next
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