Q: How do I determine my basal body temperature coverline?
A: The reason for charting your temperature is to determine when and if you ovulated. Ovulation is associated with an increase in temperature -- a thermal shift -- revealing a typical biphasic curve. The coverline is a horizontal line drawn after ovulation to help differentiate temperatures before ovulation (low) and temperatures after ovulation (high). When your waking body temperature rises more than two-tenths of a degree higher than the previous six days, and it stays that way for at least two days, your coverline can be established.
Learn how to draw a coverline here.