Interest rate hike impact calculator

On a bond with 20 years left, a move from 10.50% to 10.75%, as prime did in September 2026, adds about R168 a month on R1 million, R337 on R2 million and R505 on R3 million. Actual bank terms and fees differ, so treat these as estimates.

It uses a standard amortising payment on the balance and remaining term, once at the rate before and once at the rate after. The difference is the extra per month, and the extra per year is that amount times 12.

It is for bonds, car finance and personal loans with a remaining term. Credit cards and overdrafts often reprice too, but they are not amortising instalment loans, so it does not fit them.

Your bank may use a different day count, fees or rate reset timing, so the calculator gives an estimate. It is a planning tool, not financial, credit or legal advice. The defaults follow the September 2026 prime move, and you can type any before and after rates instead.