Free Australian BBT tool
BBT Chart Annotator and Temperature Shift Checker
Turn waking temperatures into an editable chart, keep disturbed readings visible and review a possible sustained shift with a transparent optional rule.
An auditable chart, not a black-box verdict
See the sequence, disturbances and calculation together
The chart plots the temperatures you entered, marks readings that may be less comparable and shows exactly how the optional pattern check was applied. It does not use one temperature to diagnose ovulation or pregnancy.
Interactive BBT tool
BBT Chart Annotator and Temperature Shift Checker
Plot waking temperatures, annotate disturbed readings and use an optional six-plus-three pattern check without turning the software result into proof of ovulation.
Privacy: entries are processed on this device. Nothing is sent to Fertility2Family.
Your chart review
Pattern result
Next:
The chart connects comparable included readings. Excluded readings remain visible as separate grey points.
How the automatic check works
The tool needs nine consecutive cycle days. It calculates the median of six included baseline readings and checks whether the next three included readings are each at least 0.20°C higher. A missing or excluded day breaks that automatic sequence.
This is a transparent Fertility2Family software rule for organising a chart. It is not a validated diagnostic or contraception algorithm.
Use the chart for the next useful decision
A basal thermometer supports repeatable two-decimal waking-temperature tracking. BBT is retrospective, so use LH tests for fertile-window timing and pregnancy tests for hCG testing.
Quick answers
What this chart can show, and what it cannot
What counts as a sustained rise here?
Three consecutive included readings at least 0.20°C above the median of the preceding six included readings.
Does a rise prove ovulation?
No. The pattern may support a retrospective estimate, but the rule is not a diagnostic test.
Should disturbed readings be deleted?
No. Keep them visible and mark or exclude them so the chart retains the complete record.
Can one dip show implantation?
No. A single dip cannot identify implantation and should not be used as a pregnancy test.
How to use the result
Interpret the chart as a record, not a diagnosis
Why relative change matters more than one “normal” temperature
Baseline temperatures differ between people and cycles. The useful information is the sequence relative to that chart’s own baseline. Similar wake times, one thermometer and one measurement route improve comparability, while sleep, illness, alcohol, travel, stress and shift work can move individual readings.
What the optional rule adds
The tool compares six consecutive included baseline readings with the next three consecutive included readings. Each of the final three must be at least 0.20°C above the baseline median. The rule is published so the result can be reproduced, challenged and cited. It is not a validated clinical or contraception algorithm.
What to do with a messy chart
Keep unusual readings visible, record the reason and exclude them from the optional check only when appropriate. Do not fill missing days with invented temperatures. Repeated unclear charts, irregular cycles or fertility concerns are better reviewed with a GP, fertility clinic or trained fertility-awareness educator.
Connected fertility tools
Continue from a BBT pattern to the right next tool
Each tool owns one task. Use only the step that matches the information available in the current cycle.
Related evidence and next steps
Use the page that owns the next cycle question
Complete BBT charting guide
Learn how waking temperature fits with other fertility signs and cycle tracking.
Read Complete BBT charting guideWhat an implantation dip can and cannot show
Separate one temperature dip from proof of implantation.
Read What an implantation dip can and cannot showBasal thermometer Australia
Compare a reusable two-decimal BBT thermometer and current product instructions.
Compare basal thermometersAustralian fertility-awareness guidance
Read about temperature, mucus and calendar methods and their limitations.
Read Australian fertility-awareness guidanceSix useful questions
Frequently asked questions about BBT chart interpretation
How should I take BBT for cycle tracking?
Measure immediately after waking and before getting out of bed where possible. Use the same thermometer and route, record the actual time and mark poor sleep, illness, alcohol, travel, shift work or other disturbances.
How much of a rise does this tool check for?
The optional rule checks whether three consecutive included readings are each at least 0.20°C above the median of the preceding six included readings. This is a transparent software rule, not a universal clinical threshold.
Can a BBT chart confirm the exact day of ovulation?
No. BBT is retrospective. A sustained change may support an estimate that the cycle phase changed, but it cannot prove egg release or identify one exact ovulation moment.
What should I do with a disturbed BBT reading?
Keep the reading visible, record what affected it and exclude it from the optional rule when appropriate. Deleting inconvenient points can hide the measurement history.
Does a one-day BBT dip mean implantation?
No. A one-day dip can have many causes and cannot identify implantation or pregnancy. Use an appropriately timed pregnancy test to check for hCG.
Can I use this BBT rule for contraception?
No. The rule is an educational chart-organising heuristic, not a validated fertility-awareness or contraception method. Seek instruction from a qualified service for contraceptive use.
Clinically reviewed
Evan Kurzyp, Registered Nurse
Bachelor of Nursing and Master of Mental Health Nursing
AHPRA registration NMW0002424871
Reviewed: 4 August 2026. Next scheduled review: August 2027, or earlier if Australian guidance, product instructions, laboratory standards or safety advice change.
Methods, limitations and references
How the chart and optional temperature-shift rule work
The software checks every nine-day consecutive window. It calculates the median of six included baseline readings and requires the next three included readings to be at least 0.20°C higher. Missing or excluded days break the window and no points are interpolated.
The deployed version should be rechecked whenever product instructions, Australian guidance or tool logic changes.