BBT Chart

A BBT chart is a daily record of your basal, or resting, temperature taken immediately after waking and before activity. Plotting the readings across a cycle can make a lower-temperature phase and a later higher-temperature phase easier to see.

Look for a group of lower readings followed by several readings that remain above them. This chart may show a coverline and label a possible sustained rise, while missing days and unusual readings stay visible. Read the pattern over several days rather than treating one point as conclusive.

The coverline is a visual reference based on earlier lower readings. Here, it appears only when the chart has enough eligible readings and finds a possible sustained rise, helping you compare later temperatures with the prior pattern. It is not a diagnosis.

MedlinePlus describes a shift of about 0.2°F or more above the previous six days. StatPearls notes that BBT commonly rises about 0.5–1°F after ovulation. Your pattern may differ, so a sustained change matters more than any single number.

BBT mainly shows a temperature shift after it has happened, so it does not provide advance notice of your most fertile days. For a calendar-based estimate before the shift, try the [ovulation calculator](/ovulation-calculator/) and treat its dates as estimates.

No. A temperature pattern is not a diagnosis of ovulation or pregnancy, and research has found that BBT alone is not reliable for identifying ovulation timing. Use it as one retrospective clue and talk with a clinician if you need medical guidance.

Take it immediately after waking, before you sit up or get out of bed, eat, drink, or begin other activity. Aim for the same time each day and use the same measurement method.

Fever or illness, alcohol, too little or interrupted sleep, and taking your temperature at different times can change a reading. Travel, stress, and a change in measurement method may also affect consistency. Mark disruptions on the chart so you can read the surrounding pattern in context.

An implantation dip is an informal name for a one-day temperature drop that some people notice during the luteal phase. Similar dips can appear in cycles with or without pregnancy, so this pattern is not a diagnosis. Use a pregnancy test at the appropriate time rather than relying on a chart dip.

Use a basal or digital thermometer that reads to a tenth of a degree so you can see small changes. A basal thermometer can make this easier, but using the same thermometer and method each morning is also important.

Your temperatures stay in this browser and are not uploaded or sent to a server. Clearing this site's browser data or switching browsers will not carry the log with you, so export a CSV if you want a separate copy.

Yes. Use Export CSV to save a dated copy of your temperatures, units, and notes. It's a plain file you can keep as a backup or bring to an appointment. Nothing is uploaded, the export happens right in your browser.