Interest rate and property value

We assume interest rate does not change, the property value is accurate and does not decrease.

Length of month

All months are assumed to be of equal length. In reality, many loans accrue on a daily basis leading to a varying number of days' interest dependent on the number of days in the particular month.

Number of weeks & fortnights in a year

One year is assumed to contain exactly 52 weeks or 26 fortnights. This implicitly assumes that a year has 364 days rather than the actual 365 or 366.

Rounding of amount of each repayment

In practice, repayments are rounded to at least the nearer cent. However the calculator uses the unrounded repayment to derive the amount of interest payable at points along the graph and in total over the full term of the loan. This assumption allows for a smooth graph and equal repayment amounts. Note that the final repayment after the increase in repayment amount will be a partial repayment as required to reduce the loan balance to zero.