Illustration showing three ways to measure with Natural Cycles: basal thermometer, Apple Watch and the Oura Ring
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3 Ways to measure with Natural Cycles

Jen on the roof terrace at Natural Cycles headquarters.

Written by Jennifer Gray

Jennifer Gray

Jennifer Gray is an award-winning writer with more than five years’ experience covering reproductive topics ranging from birth control to planning pregnancy. She is passionate about providing women with accurate information grounded in science they can use to take charge of their own health - while also dispelling myths that exist within the field of women’s health. She holds a Master of Science from the University of Edinburgh and currently lives in Ireland.

The Natural Cycles certified algorithm uses body temperature to determine fertility, as there is a small, but detectable shift in temperature that happens after ovulation. Once the algorithm gets to know your unique cycle, it’s able to both confirm and predict the fertile window. For the NC° algorithm to learn your cycle you need to measure with one of our three devices. This article outlines how each device works and can help you find the right measuring option for you!

All compatible measuring devices have been independently evaluated and are found to have the same effectiveness when used with NC° Birth Control. However, each device works in a slightly different way and may suit different routines and preferences. Read on to find the right device for you…

1. The NC° Thermometer

Our latest thermometers are Bluetooth compatible, making it easier for morning measurers to do their thing. The thermometer is used in the morning before you get up and out of bed. It’s a great option for those who love their routine and don’t want to wear a device to bed. Measuring with our thermometer is also the most cost-effective method to use NC°, as the price of a thermometer is included with an annual NC° subscription.

How does it work?

Different from a regular fever thermometer, the NC° Thermometer is a basal thermometer designed to measure basal body temperature. This can only be measured at the body’s lowest resting temperature, after several hours of sleep. 

To get the most out of Natural Cycles, we recommend taking your temperature at least five times a week, but NC° doesn’t get less effective if you forget to measure. If you’re feeling sick or hungover, you can choose to manually exclude temperatures too. Each Bluetooth thermometer saves up to ten temperatures, meaning if you measure but forget to sync, your temperature data will be stored until you have time to input your data.

Round up

  • Best for Cyclers who love their morning routine
  • Free with NC° annual plan ($39.99 when bought separately)
  • Temperatures sync automatically to the NC° app via Bluetooth 

2. The Oura Ring

Our first wearable integration with smart ring innovators, Oura, made measuring a seamless experience. Instead of taking your temperature in the morning, with the Oura Ring, all you need to do is wear your ring to bed each night. The Oura Ring is sold separately from the NC° subscription, but Natural Cycles users get an exclusive $40 Oura discount. 

How does it work?

Unlike the thermometer, the Oura Ring doesn’t just take one reading in the morning. Instead, it measures temperature trends from your finger throughout the night while you sleep. Each Oura Ring features research-grade sensors that monitor your temperature and heart rate throughout the night. In the morning, simply sync the ring with the app and you’ll be able to see your fertility status for that day. 

Round up

  • Measures overnight while you sleep
  • Great option for snoozers and those who want to monitor sleep
  • Oura Rings start at $299, but NC° users get $40 off

3. Apple Watch

Our latest integration with Apple Watch was our most requested feature EVER. It’s another great option for those who prefer to sleep in or have more irregular sleep patterns. To use NC° with Apple Watch, you’ll need a watch model with temperature sensors, these are included from Series 8 and upwards.

How does it work?

There are two temperature sensors on the back of the watch. These measure wrist temperatures throughout the night. Simply connect your Apple Watch with Natural Cycles by following the steps in the app – and you’re good to go. Set Sleep Focus in your Apple Health app to make sure your temperature data is measured overnight, and in the morning you’ll see your temperature appear in the NC° app, no syncing required! 

Round up

  • Go from day to night with the same device
  • Measures while you sleep and syncs automatically
  • Purchase Apple Watch (with temperature sensors) separately from $399

Natural Cycles is just as effective and secure when used with Apple Watch as it is when used with an oral thermometer or an Oura Ring. Natural Cycles has FDA Clearance for use with all compatible devices, part of this certification involves demonstrating that. Keep in mind that switching devices can lead to more Red Days while the algorithm adjusts. We recommend changing your measuring device at the start of your cycle for the smoothest experience.

Making more ways to measure with Natural Cycles°

We know everyone is different, and that’s why we want to give you the choice of how you measure. We’re continually researching, testing, and innovating so we can offer you more ways to measure in the future. Our goal is to make Natural Cycles available to anyone who wants to use it! Watch this space for more measuring updates in the future!

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