Q: How do I calculate my basal body temperature coverline?

A: When your waking body temperature rises more than 0.2 or two-tenths of a
degree higher than the previous six days, and it stays that way for at
least two days, you can start drawing your coverline.

This rise normally occurs during your thermal shift the day after ovulation.
For example, a jump from 97.1 to 97.3 is a rise that is 0.2 or two-tenths of a degree higher.