Basal Body Temperature Tracking
Enter daily basal body temperatures to observe the biphasic shift associated with ovulation. The calculator suggests a coverline and highlights the first sustained rise.
Enter at least 6 days of temperatures to calculate coverline and detect shifts.
How to Use This Calculator
Measure basal temperature consistently
Take your temperature first thing each morning after at least 3–4 hours of sleep, before getting out of bed.
Enter daily readings
Record temperatures immediately. Aim for at least 6 consecutive days to establish a baseline coverline.
Interpret the shift
A sustained rise above the coverline for at least three days suggests probable ovulation. Combine with other fertility signs for accuracy.
Formula
Coverline: Baseline + 0.2°F (0.11°C), where baseline is the highest of the first six temperatures prior to the suspected ovulation rise.
Ovulation shift: Identified when three consecutive temperatures exceed the coverline.
Unit conversion: °F = (°C × 9/5) + 32, °C = (°F − 32) × 5/9.
Full Description
Basal body temperature charting helps identify ovulation by detecting the progesterone-driven thermal shift that occurs after an egg is released. Consistent measurement and interpretation of BBT patterns assist in natural family planning, fertility awareness, and monitoring luteal phase adequacy. External factors such as illness, disrupted sleep, alcohol, or medication can impact readings; note these alongside the temperature log.
Frequently Asked Questions
How many days confirm ovulation?
A sustained rise above the coverline for at least three consecutive days typically confirms ovulation has occurred.
What if I skip a temperature?
Missing an occasional reading is acceptable. Continue charting; trend analysis relies on multiple data points.
Can I use oral, axillary, or vaginal temperatures?
Yes, but keep the measurement method consistent throughout the cycle for reliable trends.
Do wearables replace manual BBT tracking?
Wearables can complement BBT tracking, but ensure device readings are calibrated and note any data irregularities.