BBT Tracking Guide: How to Use Basal Body Temperature for Fertility
By Ovuloom Team | December 22, 2025 | 12 min read
Basal Body Temperature (BBT) tracking is one of the most reliable ways to confirm that
ovulation has occurred. While it can't predict ovulation in advance for the current cycle, it helps you
understand your body's patterns and verify that you ARE ovulating.
What is BBT? Your Basal Body Temperature is your body's lowest resting temperature,
measured first thing in the morning before any activity. After ovulation, progesterone causes a slight
temperature rise (0.2-0.5°C / 0.4-1.0°F) that lasts until your next period.
How BBT Works
During your cycle, your temperature follows a predictable pattern:
Typical BBT Pattern (Ovulation on Day 14)
📈 Notice the clear shift after ovulation
(Day 14)
- Follicular Phase (before ovulation): Lower temperatures, typically 97.0-97.5°F
(36.1-36.4°C)
- After Ovulation: Temperature rises by at least 0.4°F (0.2°C)
- Luteal Phase (after ovulation): Higher temperatures, typically 97.6-98.6°F (36.4-37°C)
How to Track BBT: Step-by-Step
-
Get a BBT Thermometer
Use a basal thermometer (measures to 0.01°F) rather than a regular fever thermometer. Digital ones with
memory are convenient.
-
Take Your Temperature Immediately Upon Waking
Before getting up, talking, eating, or even sitting up. Keep the thermometer by your bed.
-
Take It at the Same Time Every Day
Consistency is key. Aim for the same time ±30 minutes each morning; sleeping late can elevate readings.
-
Record Your Temperature
Log it in the Ovuloom app or a chart. Note any factors that might affect it (illness, alcohol, poor
sleep).
-
Look for the Shift
After 3 consecutive days of higher temperatures, you can confirm ovulation occurred. This is called the
"coverline."
Pro Tip: Track for at least 3 cycles before relying on the data for conception timing. This
helps establish YOUR personal baseline and patterns.
Interpreting Your BBT Chart
What a Healthy Chart Looks Like
- Clear biphasic pattern (two temperature levels)
- Temperature shift of at least 0.4°F (0.2°C)
- Luteal phase (high temps) lasting 12-16 days
- Temperature drops when period starts
Signs You May Not Be Ovulating
- No clear temperature shift
- Erratic temperatures throughout the cycle
- Short luteal phase (less than 10 days of high temps)
Important: BBT confirms ovulation AFTER it happens. By the time you see the temperature
rise, your fertile window has passed. For conception timing, combine BBT with other methods like cervical
mucus tracking or OPKs.
Factors That Can Affect BBT
- Illness or fever
- Alcohol consumption the night before
- Disrupted sleep or sleeping at different times
- Traveling across time zones
- Using an electric blanket
- Stress
When any of these occur, note it in your chart. Most apps let you mark "disturbed" temperatures.
BBT and Pregnancy
If you're pregnant, your temperature stays elevated past your expected period. 18+ days of high
temperatures with no period is a strong early pregnancy sign!
Why Use an App for BBT Tracking?
Apps like Ovuloom automatically:
- Create your temperature chart
- Detect temperature shifts using algorithms
- Combine BBT with other fertility signs for better predictions
- Store months of data for pattern analysis
- Alert you to potential issues
Ovuloom