Basal Body Temperature Chart Calculator
Analyze BBT readings to detect ovulation confirmation, luteal phase length, and cycle phase patterns.
Results
Visualization
How It Works
BBT charting confirms ovulation after it occurs. Progesterone released after ovulation raises body temperature by 0.2-0.5°F, creating a biphasic pattern.
The Formula
Temperature Shift = Post-Ovulation Avg - Pre-Ovulation Avg
Luteal Phase = Cycle Length - Ovulation Day
Variables
- BBT — Basal Body Temperature — taken first thing in the morning before any activity
- Biphasic — A clear two-phase pattern — lower temps before ovulation, higher after
Worked Example
Pre-ovulation avg 97.3°F, post-ovulation avg 97.8°F = 0.5°F shift. Adequate shift confirming ovulation.
Practical Tips
- Take your temperature at the same time every morning, before getting out of bed.
- A shift of at least 0.2°F (0.11°C) sustained for 3+ days confirms ovulation.
- BBT only confirms ovulation after it happens — it does not predict it.
- A luteal phase shorter than 10 days may indicate a luteal phase defect.
- Illness, alcohol, and disrupted sleep can cause temperature anomalies.