What this calculator does

Runs a month-by-month amortisation simulation of your bond under two scenarios — your current path (base) and an optimised path with your chosen strategies. Strategies can be stacked: extra monthly payments, annual lump sums, once-off windfalls, a rate change simulation, an annual step-up on your extra payment, and an access bond offset. The comparison shows how much interest you save and how many months sooner you become bond-free.

How the access bond works

An access bond (also called a flexi bond) lets you park extra money against your bond. The parked amount reduces your interest-bearing balance each month, saving you interest — but you can withdraw it any time. This calculator models the interest saving from keeping a constant amount parked. Available on FNB Flexi, Standard Bank AccessBond, Absa FlexiReserve, and Nedbank HomeSaver bonds.

Assumptions applied

• The base monthly payment is fixed throughout both simulations — strategies add extra cash on top, not change the required payment.
• Interest rate is assumed constant (except when a rate change strategy is active).
• Access bond: the parked amount is assumed to remain constant. Withdrawals are not modelled.
• Annual lump sums are applied each year at the chosen calendar month.
• Once-off lump sums are applied at the end of the chosen year.
• Annual step-up adds to your extra payment at each 12-month interval.
• Simulations use a safety cap of 2× the original term to handle edge cases.

What this calculator doesn't account for

• Does not account for bank-specific access bond features, minimum balance requirements, or withdrawal restrictions.
• Does not model variable interest rates (prime rate movements) during the loan term.
• Does not include admin fees or other bond costs.
• Strategy breakdown shows each lever in isolation — the combined saving may differ from the sum of individual savings due to compounding interactions.