I moved from Oregon to Texas and paid OR state taxes for several months before changing W2 with my company. HOw do I calculate my OR taxes

File a part-year resident return with Oregon. On that return you will report the date when you moved out, and calculate taxes owed to OR only for the income you earned while an OR resident. Given that you continued to pay OR withholding even after moving away you will probably get a nice refund from them.

Once again, ebaines has it right.

Every tax software available allows for filing a part-year return. The calculations are grade school math.