Calibrating Friction Factors. At least some of the illustrative embodiments are methods including: calibrating friction factor for a drilling operation by: plotting on a display device the expected hook load versus depth for the drilling operation; displaying plot points on the display device, each plot point indicative of a measured hook load versus depth for the drilling operation; selecting a plot point associated with a depth, the selecting responsive to a cursor hovering over the plot point on the display device; displaying a friction factor values which correlates the expected hook load versus depth for the particular depth to the measured hook load versus depth for the plot point, selecting the value responsive to the cursor hovering over the value; and then shifting on the display device at least a portion of the indication of expected hook load versus depth based on the value of friction factor.