--- title: "Basal body temperature: what it tells you about your cycle (and what it doesn't)" description: "A cheap thermometer and three minutes each morning can tell you a lot about your cycle. But BBT mostly confirms, it doesn't predict. Here's how to use it smartly." url: https://myperiod.app/en/blog/basale-lichaamstemperatuur-cyclus lang: en date: 2026-06-16 publisher: PERIOD. B.V., Amsterdam --- [Back to blog](https://myperiod.app/blog) [Your cycle](https://myperiod.app/blog/categorie/cyclus) · 6 min read # Basal body temperature: what it tells you about your cycle (and what it doesn't) [Lees dit artikel in het Nederlands](https://myperiod.app/blog/basale-lichaamstemperatuur-cyclus) PERIOD. team · June 16, 2026 Basal body temperature (BBT) is your body temperature in complete rest, taken right after waking, before getting up, drinking or moving. During a natural cycle it follows a recognizable pattern: lower in the follicular phase, a rise after ovulation, and elevated throughout the luteal phase. ## The pattern in one paragraph Before ovulation, estrogen dominates. BBT typically sits between 36.2 and 36.5 °C. After ovulation, progesterone rises and BBT goes up by about 0.2 to 0.5 °C. That higher plateau holds until just before menstruation. If no pregnancy follows, progesterone drops and so does temperature. ## What BBT reliably tells you - **Whether you actually ovulated.** No sustained rise after an expected ovulation = likely no ovulation that cycle. - **The length of your luteal phase.** Count from the clear temperature rise to your first day of bleeding. A short luteal phase ( - **Predict when you'll ovulate.** The rise happens after ovulation. To predict, combine BBT with cervical mucus and/or LH tests. - **Work as standalone contraception.** Methods that use BBT (FAM, symptothermal) require training and discipline and have considerably higher typical-use failure rates than long-acting methods. - **Work as expected on the pill or shortly after stopping.** Hormonal contraception suppresses ovulation, so no biphasic pattern appears. ## How to measure properly - Use an **actual basal thermometer** (two decimal places). A fever thermometer is too coarse. - Measure **at roughly the same time every morning**, immediately on waking, before getting up. - Measure **after at least 3-4 hours of uninterrupted sleep**; less is unreliable. - Pick one site (oral, vaginal or rectal) and stay consistent. Vaginal and rectal are usually more stable than oral. - Note disruptors: illness, alcohol the previous night, short night, jet lag, room much warmer or colder than usual. > This isn't medical advice. Questions about fertility or contraception? See your doctor. ## What a "clean" BBT chart looks like A typical biphasic chart shows roughly two weeks of slightly lower temperatures, then a clear "shift" upward of at least 0.2 °C that stays higher for at least 3 consecutive days. Then the higher plateau holds for 10 to 14 days, until menstruation begins and values drop again. ## What an unusual pattern might mean - **No clear rise:** possibly an anovulatory cycle. - **Short rise ( Your daily temperature, mucus observations and mood form a remarkably detailed portrait of your health. That's exactly the kind of data that shouldn't leak via ad networks. PERIOD. logs it all encrypted on EU servers, with no ad trackers. Read: [privacy policy](https://myperiod.app/privacy) and [a cycle app that doesn't sell data](https://myperiod.app/blog/cyclus-app-zonder-data-verkopen). Read also: [recognizing ovulation symptoms](https://myperiod.app/blog/ovulatie-symptomen-herkennen) and [the four phases of your cycle](https://myperiod.app/blog/vier-fasen-van-je-cyclus). [Download PERIOD. on the App Store](https://apps.apple.com/us/app/period-cycle-period-tracker/id6757947793) · [via Google Play](https://play.google.com/store/apps/details?id=app.myperiod.android). Want to understand your cycle better? ## Keep reading [Best app for period and ovulation tracking (2026)Tracking your period and ovulation in one app: what an app can and cannot know, which measurements really help, and how Flo, Clue, Natural Cycles and PERIOD. approach it.Read more](https://myperiod.app/blog/best-app-period-and-ovulation-tracking)[Trying to conceive: when do you switch from a cycle app to a pregnancy app?Short answer: preferably never. The moment you switch is exactly when your cycle data is worth the most. What you lose, what you need, and how it fits in one app.Read more](https://myperiod.app/en/blog/van-cyclus-app-naar-zwangerschapsapp-wanneer-overstappen)[Cycle app on the pill: is tracking still worth it when you use contraception?Short answer: yes, but for a different reason than you think. On the pill you do not predict ovulation, but you do track complaints, bleeding and what happens when you stop.Read more](https://myperiod.app/en/blog/cyclus-app-met-de-pil-heeft-het-zin)