If you thought thermometers were only useful to check whether or not you had a fever, think again.

An ovulation thermometer can also provide important information about a woman’s fertility – when she’s most likely to ovulate, which might help increase her chances of getting pregnant. Conversely, some women use it as a birth control method, avoiding pregnancy and sex when ovulation is likely.

Ovulation thermometers measure a woman’s basal body temperature (BBT). BBT is the lowest temperature your body reaches during rest. In women, this temperature can change due to hormonal fluctuations during the menstrual cycle, and it can be used to predict ovulation because ovulation causes a slight increase in basal body temperature.1,2

The basal body temperature method can also be used to detect pregnancy. Following ovulation, a rise in basal body temperature that lasts for 18 or more days may be an early indicator of pregnancy.1

It’s important to note that you’ll also need a special basal or ovulation thermometer. These thermometers show two decimal places. Normal thermometers may only show one decimal place, and the changes in your temperature will be really small — fractions of a degree (0.3).1,3

It’s also important to follow a strict process when trying to predict fertility:1,2

  • Take your basal body temperature with a specifically designed ovulation BBT thermometer every morning before getting out of bed
  • Try to take your temperature at the same time each day, when you first wake up
  • Track your temperature readings. Record your daily basal body temperature and look for a pattern to emerge. You can use a paper diary/calendar or a quick search will no doubt find an app
  • Track for at least 3 menstrual cycles for better accuracy2
  • Basal body temperature may increase slightly — typically less than a 0.3oC when you ovulate. When the slightly higher temperature remains steady for three days or more, that is probably the time of ovulation
  • Plan accordingly – you’re most fertile about two days before your peak BBT, but remember, sperm can live up to five days. If you’re trying to get pregnant, this is the best time to have sex. If you’re trying to avoid pregnancy, don’t have unprotected sex from the beginning of your menstrual period until your BBT rises

Welcare has just introduced a specifically designed Ovulation Thermometer that is very affordable, ticks the boxes of accuracy and sensitivity, with readings to two decimal places. It is available at all leading pharmacies and online. Learn more here.

*Always read the label and follow the directions for use.


  1. https://www.mayoclinic.org/tests-procedures/basal-body-temperature/about/pac-20393026
  2. https://my.clevelandclinic.org/health/treatments/21065-basal-body-temperature
  3. https://www.plannedparenthood.org/learn/birth-control/fertility-awareness/whats-temperature-method-fams