Repayments are calculated using the standard amortization formula — the same one your bank uses. For an interest-only loan, monthly repayments during the IO period equal interest on the full loan balance; once the IO period ends, repayments rise to fully repay the loan in the remaining term.

Offset accounts reduce the interest-bearing balance dollar-for-dollar. We assume the offset balance you enter is held for the full life of the loan (in practice, your average balance varies).

Extra repayments apply on top of the regular repayment and reduce the loan balance immediately, shortening the loan term and saving interest.