The BBT method is based on the body's physiological response to hormonal changes during the menstrual cycle. Before ovulation, a woman's basal body temperature typically ranges from 97.0 to 97.5°F (36.1 to 36.4°C). After ovulation, due to the hormone progesterone, the BBT rises by about 0.5°F (0.3°C) and remains elevated until the next menstrual period. By charting these temperature changes over several cycles, women can identify patterns and predict ovulation.
