Oura has taken steps to validate the accuracy of its Fertile Window feature, using its smart ring in a study to prove its credentials as an ovulation detector.
The research, conducted by in-house scientists at Oura and published in the Journal of Medical Internet Research, established the Oura Ring and Fertile Window as significantly more accurate than the traditional calendar method.
Fertile Window leverages the ring’s continuous finger temperature data and the brand’s proprietary algorithm to detect ovulation changes, peak fertility, chance of conception, and predicted ovulation day – as well as detect ovulation. This was tested against the traditional calendar method, which relies on estimations based on menstrual cycle history.
The study revealed that the Oura Ring significantly outperformed the calendar method, detecting 96.4% of ovulations with an average error of just ±1.26 days. The calendar method, on the other hand, posted a ±3.44 day average error.
Interestingly, the smart ring’s improved accuracy was also observed across participants regardless of age, menstrual cycle length, or cycle regularity. And findings may prove particularly useful for those with irregular cycles.
For these participants, Oura Ring’s Fertile Window produced an average error of only 1.48 days, in contrast to the calendar method’s 6.63-day error.
Wareable’s view:
If the last year or two have taught us anything, it’s that Oura isn’t afraid to run features through a scientific test to enhance their validity. And while it’s fair to be skeptical about tests conducted by in-house scientists, the findings remain a significant milestone for Fertile Window.
The feature was released in October 2024 as part of a general update to Cycle Insights’ accuracy, and clearly shows it as a more personalized and reliable way to predict ovulation than one of the most common low-tech methods.
And while it’s far from the only wearable using biometrics for ovulation tracking, this study also showed it to be more effective than the Apple Watch. It slightly bested the smartwatch when predicting typical cycle participants (1.53 versus Oura’s 1.18 MAE) and atypical ones (1.91 versus Oura’s 1.70).
If last year’s near-monthly feature releases are a reference, this may not be the only new-ish Oura feature to be validated by further study. With the latest Gen 4 ring boasting improved sensor pathways, expect to hear plenty more about Oura’s health-tracking credentials in 2025.
