The attached documents explain why we show IBC and not IRC in the BC Calc® software. One is for the 2012 IBC and the others are for the 2015 IBC reference.
BC Calc® Building Code Reference 2012 IBC IRC Memo
BC Calc® Building Code Reference 2015 IBC IRC Memo
BC Calc® Building Code Reference 2018 IBC IRC Memo
BC Calc® Building Code Reference IBC ASCE 2015 IRC Memo
For further information you may contact EWP Engineering Support: 800-232-0788