Areal reduction factors (ARFs) are used in New Zealand to convert rainfall measurements from one point to an entire area. Different methods were used to estimate ARF values in Christchurch and Auckland, with the USWB and Bell's methods showing the most realistic results. ARF values were found to be higher in Christchurch compared to Auckland, possibly due to differences in topography and storm patterns. Bell's method, which considers return period, is recommended for design purposes in these cities. More data from additional locations is needed to improve the estimation of ARF values nationwide.