Basal Body Temperature Calculator
BBT Shift Analysis
Analyze pre- and post-ovulation temperatures to detect a thermal shift
°F
°F
°F
°F
BBT Temperature Converter
Convert basal body temperature between Fahrenheit and Celsius
Formula
Coverline = Pre-Ovulation Average + 0.1°F | Thermal Shift = Post-Ovulation Average - Pre-Ovulation Average | Ovulation confirmed if 3 consecutive temps above coverline with shift >= 0.2°F
Frequently Asked Questions
What is a basal body temperature shift?
A BBT shift is a sustained rise in resting body temperature (typically 0.2-0.5°F) that occurs after ovulation due to the hormone progesterone. When your temperature stays elevated for at least 3 consecutive days above the coverline, ovulation is confirmed.
When should I take my basal body temperature?
Take your BBT first thing in the morning before getting out of bed, talking, or eating. Use a BBT thermometer (accurate to 0.01°F) and take it at the same time each day. At least 3 hours of uninterrupted sleep is recommended for accuracy.
Can BBT predict ovulation in advance?
BBT alone cannot predict ovulation before it happens — it only confirms ovulation after the fact via the thermal shift. To predict ovulation, combine BBT with cervical mucus monitoring or OPK (ovulation predictor kit) testing.
You may also need
H
Luteal Phase Calculator
Calculate your luteal phase length from cycle and ovulation data. Identify potential luteal phase defects and understand your fertility window timing.
HealthH
Clomid Ovulation Calculator
Predict ovulation timing when taking Clomid (clomiphene citrate). Estimate your fertile window based on when you started Clomid and your cycle day.
HealthH
Period Calculator
Free period calculator. Predict your next menstrual period, track cycle regularity, and estimate upcoming periods based on your cycle history.
Health