Insulation R Factor/savings calculation?

Does anyone know if there is a good way to calculate the predicted savings in adding additional insulation to a home?
I recently blanketed my attic in R-33 fiberglass. I installed this over the existing R-9 or R-12 that appears to have been up there, along with some blown insulation.
I want to see if there is a good way to calculate the possible expected savings in heat loss and or home heating savings.
Anyone? Thanks.

See original post by Mia