How accurately the Ultrahuman Ring predicts the start of your next period
TEMPERATUREOPTICAL
Accuracy
3.7 days
Period Prediction Error
in irregular cycles, and 2.2 days when they are regular
Reference standard
The day the period arrived
Sample size
24,476 members
The Ultrahuman Ring predicts the start of the next period to within 3.7 days when cycles are irregular, and 2.2 days when they are regular.
2.2 daysregular cycles
3.7 daysirregular cycles
79%all cycles, within 3 days
90%all cycles, within 5 days
A cycle that arrives when it likes is one of the most common reasons people start tracking in the first place, and it is also the case where calendar maths is least use. So the fair test is to put the prediction next to the day the period actually arrived, and to do it separately for women who reported at onboarding that their cycles are regular and women who reported that they are not.
The prediction was tested on 86,885 cycles from 24,476 members. In women who report irregular cycles the start date was predicted to within 3.7 days, and in women with regular cycles to within 2.2 days.
Across all cycles taken together, the prediction lands within three days 79% of the time and within five days 90% of the time.
The Possible Anovulation cycle flag has also been reported to show up more often in irregular cycles than in regular ones, and to do so across every age group — see Temperature-derived Cycle Flags™.