BBT chart examples: five patterns to compare
Updated July 2, 2026
This gallery compares five BBT chart examples: a textbook biphasic cycle, a pregnancy chart with sustained temperatures, a triphasic chart, a flat anovulatory chart, and an implantation dip. In Fertility Friend's published chart analysis, a one-day dip appeared in about 23% of pregnancy charts versus 11% of non-pregnancy charts. No chart confirms pregnancy. Only a pregnancy test or a clinician can.
Key takeaways
- A normal ovulatory chart is biphasic: lower temperatures before ovulation, then a sustained rise of about 0.4 to 1.0 F afterward.
- Temperatures that stay high well past your expected period are the pattern people watch for, but they are a clue, not proof.
- A triphasic chart shows a second rise later in the luteal phase. It happens in some pregnancy and some non-pregnancy cycles.
- A flat chart with no sustained shift can mean ovulation did not happen that cycle (an anovulatory cycle).
- An implantation dip is one lower day mid-luteal phase. It is common in cycles that are not pregnant too.
Every chart below is an illustrative example built for this page, not real user data. Before you scroll, three quick terms make each one easier to read. The coverline is a reference line drawn just above your pre-ovulation temperatures. The thermal shift is the jump up to your higher post-ovulation range. DPO means days past ovulation, so 8 DPO is the eighth day after you ovulated. Tap or hover any dot to see that day.
1. What does a normal biphasic ovulatory chart look like?
What to notice: two clear levels. Temperatures sit low through the first half of the cycle, then step up after ovulation and stay up until just before the period, when they start to fall. The shift here is about half a degree and holds above the coverline for the whole luteal phase. This is the baseline every other pattern is compared against. If you are new to charting, this is the pattern to learn first; the pregnant vs not pregnant comparison builds on it.
2. What does a pregnancy BBT chart look like?
What to notice: toggle between the two examples. The first cycle keeps its temperatures elevated past cycle day 28, with no pre-period drop, because progesterone stays high. The second cycle looks identical until the luteal phase ends and temperatures fall as the period begins. The luteal phase runs about 14 days, so temperatures that stay high roughly 16 or more days after ovulation are the sustained high pattern people look for. It is a hint worth testing on, not a diagnosis. See the full side by side comparison on the pregnant vs not pregnant chart page, and the 18 day rule for when high temps become meaningful.
3. What is a triphasic BBT chart?
What to notice: three levels instead of two. There is the pre-ovulation low, the usual rise after ovulation, then a second smaller rise later in the luteal phase, marked here around cycle day 23. About 12% of pregnancy charts are triphasic in Fertility Friend's published analysis, but plenty of non-pregnancy cycles show it too, so on its own it does not tell you much. The dedicated triphasic chart page walks through the timing.
4. What does an anovulatory (flat) chart look like?
What to notice: no two levels at all. Temperatures wander up and down between about 97.0 and 97.6 F all cycle with no sustained shift, which is why there is no coverline to draw. A flat chart like this can mean ovulation did not happen that cycle. One anovulatory cycle now and then is common and not usually a concern, but frequent flat cycles are worth mentioning to a clinician. If your charts look like this often, bring a few of them to a clinician; they tell the story better than memory can.
5. What does an implantation dip look like on a chart?
What to notice: in the first example, one lower day interrupts the high luteal phase, here at cycle day 22, then temperatures climb back up. Implantation usually happens 6 to 12 days past ovulation, most often 8 to 10, which is when a dip like this would land. The second example has no dip at all and still follows a normal luteal phase. Because the dip shows up in roughly 23% of pregnancy charts and 11% of non-pregnancy charts, a single low day is a maybe, not an answer. Read the full breakdown on the implantation dip page.
See your own pattern, not just an example
Safr charts your temperatures and cycle so the biphasic shift, the coverline, and each luteal day are laid out for you day by day.
How do these BBT chart patterns compare?
| Chart pattern | Shape | What it can suggest | What it does not prove |
|---|---|---|---|
| Biphasic | Low then a sustained higher level | Ovulation likely happened | Nothing about pregnancy on its own |
| Pregnancy (sustained) | Temperatures stay high past the expected period | Worth taking a test | It is not confirmation |
| Triphasic | A second rise later in the luteal phase | Seen in some pregnancy cycles | Common in non-pregnancy cycles too |
| Anovulatory (flat) | No sustained shift, temperatures oscillate | Ovulation may not have happened | One flat cycle is not a diagnosis |
| Implantation dip | One lower day mid-luteal phase | Can line up with implantation timing | Happens in cycles that are not pregnant |
If a chart has you wondering whether it is time to test, the am I pregnant quiz does the timing math on your cycle and gives you the earliest date a home test is likely to be reliable.
Common questions
Can a BBT chart tell me if I am pregnant?
No. A chart can show whether you likely ovulated and whether your temperatures are staying high longer than usual, which is a reason to take a test. It cannot confirm pregnancy. Only a home pregnancy test, which detects the hormone hCG, or a clinician can do that. hCG typically becomes reliably detectable around the time of your missed period.
What is the difference between a pregnancy chart and a normal luteal phase?
They look the same at first. Both show a thermal shift after ovulation. The difference shows up at the end: a non-pregnancy chart drops as the period starts, usually around 14 days after ovulation, while temperatures that stay elevated past that point are the sustained pattern people watch. The only way to know is a test.
How many days of high temperatures suggest pregnancy?
The luteal phase is about 14 days, so many charters watch for temperatures that stay high about 16 or more days past ovulation with no period. That is a common prompt to test. It is a timing cue based on your own cycle, not a guarantee, and cycles vary from person to person.
Does a flat chart mean something is wrong?
Not usually. A flat chart with no sustained shift often means ovulation did not happen that cycle, which most people experience occasionally. Stress, illness, travel, or coming off hormonal birth control can all cause it. If your charts are flat month after month, or your cycles are very irregular, it is worth talking to a clinician.
Is a triphasic chart a reliable pregnancy sign?
No. A second rise later in the luteal phase appears in about 12% of pregnancy charts in Fertility Friend's published analysis, but it also shows up in cycles that are not pregnant. It is interesting to spot, but you cannot read pregnancy into it by itself. Use timing and a test instead.
How accurate does my temperature need to be for these patterns?
Take it at the same time each morning, before getting up, with a basal thermometer that reads to a hundredth of a degree. What matters is the overall shape across the cycle, not any single reading. One odd day from a short night or a late measurement is normal noise, which is why coverlines and sustained shifts look at the trend.
Keep reading
Go deeper on each pattern: pregnant vs not pregnant, the triphasic chart, the implantation dip, the fallback rise, the slow rise, and the 18 day rule. Wondering whether to test yet? Try the am I pregnant quiz.
Sources
- Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-1799.
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. N Engl J Med. 1995;333(23):1517-1521.
- Steward K, Raja A. Physiology, ovulation and basal body temperature. StatPearls. 2023.
- American College of Obstetricians and Gynecologists. The menstrual cycle. ACOG patient resources. Accessed July 2026.
- NHS. Doing a pregnancy test. nhs.uk/pregnancy/trying-for-a-baby/doing-a-pregnancy-test/. Accessed July 2026.
- Fertility Friend. Chart analysis: temperature dips and triphasic patterns in pregnancy and non-pregnancy charts. Published chart study. Accessed July 2026.
- Su HW, Yi YC, Wei TY, Chang TC, Cheng CM. Detection of ovulation, a review of currently available methods. Bioeng Transl Med. 2017;2(3):238-246.