Basal Body Temperature Chart Generator
Log Your Daily BBT
Record your temperature, cervical mucus, and OPK result each morning before getting out of bed
Pre-ovu: 36.1–36.7°C | Post-ovu: 36.7–37.3°C
Please enter a valid temperature and select a cycle day.
BBT Chart
How Does BBT Charting Work?
Basal body temperature (BBT) is your body's lowest resting temperature, measured first thing in the morning before any activity. After ovulation, the hormone progesterone causes a subtle but consistent rise of 0.2–0.5°C (0.3–0.9°F) that persists for the rest of your cycle.
By tracking this shift over several cycles, you can identify your ovulation pattern, confirm when ovulation occurred, and understand the length of your luteal phase. The coverline is drawn 0.05°C above your highest pre-ovulation temperature — three consecutive readings above it confirm ovulation.
Combine BBT with cervical mucus (CM) observations and OPK results for the most accurate fertility picture. Peak egg-white cervical mucus typically appears 1–2 days before the temperature shift.
Frequently Asked Questions
Take your temperature at the same time every morning before getting out of bed, speaking, or drinking — ideally after at least 3 consecutive hours of sleep. Even a 30-minute variation in wake time can affect your reading. A digital basal thermometer reading to two decimal places gives the most accurate data.
The coverline is a horizontal reference line drawn across your chart to identify the post-ovulation temperature shift. This tool calculates it as 0.05°C (0.1°F) above the highest temperature recorded in the six days before the detected shift. Three or more consecutive readings above the coverline confirm ovulation has occurred.
Illness, fever, alcohol the night before, a restless sleep, taking your temperature later than usual, or sleeping with an electric blanket can all produce an unusually high reading. Mark these days as disturbed and use your surrounding readings to interpret your chart.
BBT alone should not be used as contraception — it only confirms ovulation after it has occurred. As part of a broader Fertility Awareness Method (FAM) alongside CM observation, it can be effective, but requires training from a qualified fertility awareness educator.
Most practitioners recommend tracking for at least 3 cycles to identify your personal ovulation pattern, luteal phase length, and typical temperature ranges. One cycle is useful but may not be representative — stress, illness, or travel can distort individual cycles.
This tool is for informational purposes only and does not constitute medical advice. BBT charting should not be used as a sole method of contraception. Always consult your healthcare provider for personalised fertility guidance.