Blair said splitting the rates would help make it easier for people to assess what options were available to match their circumstances.
The bank also announced a cut to its standard floating rate to 5.64 per cent for those with 20 per cent or more equity and who get their salary paid into a Westpac account.
The rate is 11 basis points lower than its choices floating rate of 5.75 per cent and 60 basis points lower than its standard rate of 6.24 per cent.
Blair said as conjecture on when the official cash rate might move continued, more customers were looking at their options and breaking up their loan to take advantage of rate certainty (fixed) and repayment flexibility (floating).
"Our new floating rate is highly competitive and offers customers who are now considering splitting their home loans between fixed and floating real value," Blair said.
The bank says its rate is market leading. According to Interest.co.nz it is 1 basis point lower than Kiwibank's 5.65 per cent floating rate.