The following links provide tools to calculate the HST payable on the purchase of a new home or determine the actual price of a new home if the HST has been included in the listing price.
HST calculator - determines the HST payable as well as BC Property Transfer Tax and new housing rebates (Microsoft Excel). Based on a calculator provided in BC by the Canada Revenue Agency.
Rosborough & Company - real estate lawyers - HST calculators PLUS scroll down to the bottom of their page to find a reverse calculator, which determines the price before HST, when you only know a price that includes HST.
NOTE: These calculators do not include any provincial transitional rebates that may be applicable.