BBT Calculator | Basal Body Temperature
Adjust your basal body temperature based on measurement timing for accurate fertility tracking
Calculate Adjusted BBT
Time you normally take your BBT reading
Time you actually took today's reading
Your actual temperature reading this morning
BBT Adjustment Results
Time Analysis
Cycle Phase Interpretation
Temperature may indicate ovulation is occurring or has just occurred
Formula used: Temperature difference = (time difference ÷ 30) × 0.05°C
Adjustment rationale: Body temperature rises approximately 0.05°C every 30 minutes after waking
Medical Disclaimer
BBT tracking should NOT be used as a birth control method. Temperature can be affected by illness, travel, irregular sleep, alcohol, and many other factors. This calculator provides adjustments for timing variations but cannot account for all variables. For fertility planning or contraception, consult with a healthcare provider about more reliable methods.
BBT Temperature Ranges
Follicular Phase
36.1-36.4°C (97.0-97.5°F)
Pre-ovulation lower temperatures
Ovulation
36.4-36.7°C (97.5-98.1°F)
Temperature rise indicates ovulation
Luteal Phase
36.7-37.0°C (98.1-98.6°F)
Post-ovulation higher temperatures
BBT Tracking Tips
Take temperature immediately upon waking, before getting up
Use the same thermometer and measurement site daily
Aim for the same time daily (within 30 minutes)
Get at least 3 hours of uninterrupted sleep before measuring
Note factors that may affect temperature (illness, alcohol, stress)
Understanding Basal Body Temperature
What is BBT?
Basal Body Temperature (BBT) is your body's temperature at rest after at least 3 hours of sleep. It's measured immediately upon waking before any physical activity. BBT changes throughout your menstrual cycle due to hormonal fluctuations, particularly progesterone.
How BBT Changes During Your Cycle
- •Follicular Phase: Lower temperatures (36.1-36.4°C)
- •Ovulation: Temperature dip then sharp rise
- •Luteal Phase: Higher temperatures (36.7-37.0°C)
- •Pregnancy: Temperature remains elevated
Time Adjustment Formula
Temperature Adjustment = (Time Difference ÷ 30) × 0.05°C
Where time difference = usual time - actual time (in minutes)
Factors That Affect BBT
- Sleep: Less than 3 hours or interrupted sleep
- Illness: Fever or infection
- Alcohol: Consumption the night before
- Travel: Time zone changes
- Stress: Physical or emotional stress
- Medications: Some drugs can affect temperature
Important: BBT is most effective when combined with other fertility signs like cervical mucus observation and ovulation predictor kits.