as an extremely rough estimate
your gain is the $312K less the $180K + the depreciation you took or should have taken
say that's $30K so your gain is $162 k of which the $30K will be tax at about 25% and $132k will be tax at about 20%
if you made capital improvements from the date of purchase that would increase your basis and reduce the gain. if made these improvements should have been depreciated along with the original cost (less the amount that should have been allocated to land)
your other income for the year of sale could greatly affect the above estimate
for ex
