Free cycle tool

Printable BBT Chart

A blank basal body temperature chart, drawn to the scale you actually use. Pick Celsius or Fahrenheit, set the range so your readings land in the middle of the paper, and print one page per cycle.

Runs entirely in your browser. No account, no email, and nothing you type is sent anywhere.

Build the chart
Unit

One row every 0.05 °C. The whole scale is redrawn when you switch.

Temperature range
Grid rows
25
rows, 0.05 °C apart

Set the range so your own readings land in the middle of the paper. The shift you are looking for is a few tenths of a degree, so it only shows when it has room.

Cycle days
Paper
Both print landscape.
Rows under the grid

A temperature chart looks backwards. ACOG puts it plainly: basal body temperature "shows only when ovulation has already occurred, not when it is going to occur". The rise comes after the event — roughly 0.2 to 0.5 °C, which ACOG gives as 0.5 to 1 °F — so a chart confirms in hindsight. It cannot see one coming.

And it misses more than the textbook charts suggest. Measured against LH-confirmed ovulation across 193 cycles, a temperature shift was detected in under a quarter of them. That is a reason to read a chart across several cycles rather than to read one flat month as proof of anything.

This is not contraception. Fertility awareness has to be taught properly and combines several signs; followed imperfectly it is about 76% effective, meaning 24 women in 100 get pregnant in a year, and the NHS does not officially recommend any app or device for it. If avoiding or planning a pregnancy is the point, talk to a doctor, nurse or pharmacist rather than starting from a blank sheet.

Take the reading at the same time every morning, before you get up, eat, drink or move about much. The consistency of the time is what makes two readings comparable — one taken two hours later is a different measurement.

How this is worked out

  1. The grid is drawn from the temperature range you choose, in steps of 0.05 °C or 0.1 °F — fine enough to plot the shift, coarse enough to stay legible on one page.
  2. Cycle day 1 is the first day of bleeding. The chart runs for as many cycle days as you set, so a longer cycle still fits on a single sheet.
  3. The coverline is drawn by you, after the fact, once a sustained rise is visible. The chart leaves the row for it rather than printing one, because a coverline placed in advance would be a guess about a temperature you have not taken.
Questions

The short answers

Most waking temperatures sit somewhere between about 36.0 and 37.2 °C, or about 96.8 and 99.0 °F. Start with the default range, and if your own readings crowd the top or bottom edge, move the range and print a fresh sheet — the shift you are looking for is only a few tenths of a degree, so it is only readable when it has room to show.
Both. The unit switch redraws the whole scale, including the step size, so a Fahrenheit chart is not a converted Celsius one with awkward numbers down the side.
At the same time every morning, before you get up, eat, drink or move about much. The reading you want is the resting one, and it is the consistency of the time that makes the chart readable — a temperature taken two hours later is a different measurement.
No, and this is the single most important thing to understand about the method. ACOG puts it flatly: basal body temperature shows only when ovulation has already occurred, not when it is going to occur. The rise — roughly 0.2 to 0.5 °C, or ACOG's 0.5 to 1 °F — comes afterwards. A chart confirms in hindsight; it cannot see one coming. Kits that detect the hormone surge look forward; temperature looks back.
Less reliable than the neat textbook charts suggest. When researchers compared temperature against LH-confirmed ovulation across 193 cycles, a basal body temperature shift picked up under a quarter of them. That is not a reason to stop charting — a chart kept over several cycles still shows you a pattern — but it is a reason not to treat one flat month as proof of anything.
Not on its own, and not from this page. ACOG says outright that temperature by itself is not a good way to prevent or promote pregnancy. Fertility awareness has to be taught properly and combines several signs; followed imperfectly it is about 76% effective, meaning 24 women in 100 get pregnant in a year, and the NHS does not officially recommend any app or device for it. If that is your goal, speak to a clinician rather than charting from a blank sheet.
A horizontal line drawn just above the cluster of temperatures from before the rise, used to make the shift obvious at a glance. It is drawn after several higher readings in a row, never in advance — which is why this sheet leaves the row blank for you.

Where this comes from

  1. American College of Obstetricians and Gynecologists (2023). Fertility Awareness-Based Methods of Family Planning. https://www.acog.org/womens-health/faqs/fertility-awareness-based-methods-of-family-planning
  2. PubMed Central (2022). Basal body temperature measurement and the ovulatory temperature shift. https://pmc.ncbi.nlm.nih.gov/articles/PMC9634753/
  3. PubMed Central (2018). Continuous body temperature monitoring and the fertile window. https://pmc.ncbi.nlm.nih.gov/articles/PMC6265623/
  4. PubMed Central (2021). Wrist skin temperature and basal body temperature compared against LH-confirmed ovulation. https://pmc.ncbi.nlm.nih.gov/articles/PMC8238491/
  5. NHS (2025). Periods and fertility in the menstrual cycle. https://www.nhs.uk/conditions/periods/fertility-in-the-menstrual-cycle/
  6. NHS (2025). Natural family planning (fertility awareness). https://www.nhs.uk/contraception/methods-of-contraception/natural-family-planning/

Every link above was checked when this page was last updated. Athena is not affiliated with any of these organisations, and none of them has reviewed this page. Nothing here is medical advice.

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