OvuSense logo

BBT Thermometer

Picking a BBT thermometer is a big decision. There are lots on the market, and all of them claim to help you get pregnant, so it’s important to see through the marketing and choose one that can really boost your chances of conceiving. Today, OvuSense is here to explain how they work, and help you make the informed decision you need to.

What Do They Do?

BBT Thermometer measure your ‘basal body temperature’ - the minimum temperature your body falls to when you’re asleep overnight. During an extended rest, your metabolism slows down to conserve energy, your bodily processes slow and your temperature drops. Different conditions in your body affect what the minimum temperature is that your body drops to, so if you track that low temperature every day, and you know what changes to look for, you can see when your body is going to ovulate.

What to Look For

The key indicator of ovulation is a rise above average temperature of .4 degrees celsius which is sustained for 48 hours. For some women, this is preceded by a drop of the same amount below average over three days. This makes a clearer pattern and can give you more advance warning, but it’s not universal.

What Helps?

Knowing this gives you some indicators of what makes a good choice of BBT thermometer. You need a clear, unambiguous display. A digital thermometer gives you readout you cannot misread, whereas an old-fashioned, mercury thermometer can easily be misinterpreted by a small amount - and small difference is precisely what we’re looking.

You also need to choose a thermometer that’s accurate to tenths of a degree. If it’s only accurate to whole degrees, it won’t show you the information you need. If it’s accurate to hundredths of a degree, it might provide too much evidence of small temperature changes and swamp the simple pattern you’re looking for.

Some thermometers come with attached software which can be very helpful, lifting the burden of remembering and recording the information yourself. Some of them can even automatically turn your temperature readings into a graph, making it easy to look for the patterns you need!


We provide a different solution. Our temperature sensor looks for tiny variations in your core temperature, and uses them to map your progesterone levels. This is a direct indicator of your body’s preparations for ovulation. Our clinically tested app turns that data into an advance prediction of when you will ovulate - not a simple confirmation that it’s happened. That gives you access to your full fertile window, and boosted chance of getting pregnant when you want!

Find out more about core temperature technology and fertility here