We often claim that Flo provides the most precise period and ovulation predictions for users on the market. But exactly how accurate is Flo Period Tracker? Today, we uncover the mystery of our algorithms and explain all you wanted to know about Flo accuracy.

How does Flo prediction algorithm work?

For generations, the most common and convenient method to track one’s cycle was the conventional calendar. Women simply marked the dates of their periods and calculated their fertile window, assuming they’ll ovulate around day 14. This method is fairly accurate…provided that your cycle is regular.

Unfortunately, at least 30% of women have unpredictable menstrual cycles. That’s why all the traditional calendar-based cycle prediction algorithms, including those used in the majority of period tracking apps nowadays, might be 5 or 6 days off the correct date in their predictions if you happen to have an irregular cycle.

Flo is a bit different in this regard. We use artificial intelligence, an advanced neural network to analyze everything you and your body can tell us about. As a result, your period and ovulation predictions in Flo may become up to 54.2% more accurate. Where does the number come from? Let’s dive into some science. 

How accurate is Flo app from a scientific standpoint?

To get the real Flo app accuracy numbers, we conducted a large-scale research of user data. For the purposes of this research, we assumed that a woman’s cycle is irregular if:

  • She has logged at least three previous cycles in Flo.
  • The difference between the shortest and the longest cycles she logged is at least 7 days.

The total number of cycles we selected for the research was 971110. Approximately in half of those cycles users have logged at least one extra event — a physical symptom or a mood change.

Of those cycles, 189963 (19.6%) had at least one general or individual weak fertility predictor — i.e., a sign that points at a certain cycle stage, most often ovulation or PMS. 

Below is a great example: a user experiences acne and breast tenderness 3 to 10 days before the beginning of each cycle.

A graph showing Flo period prediction algorithm to prove its accuracy

We used the Mean Absolute Error (MAE) metric to measure the accuracy of our research. The results indicate that if a cycle has at least one weak predictor (WP) logged, the MAE of prediction accuracy was 1.59 days, while without any extra indicators it reached 2.82.

Thus, we can state that tracking symptoms regularly helps our users improve irregular cycle predictions by a whopping 43.6%. In absolute values, it shrinks the prediction window from 5.6 days to just 3.18.

How about those users who did a great job of noticing symptoms and telling Flo about them? Well, they get even more impressive Flo accuracy. Their accuracy MAE is 1.29 days. This accounts for a staggering 54.2% improvement in the accuracy of Flo app compared to the traditional calculations.

The difference in Flo app accuracy with and without logged symptoms

How accurate is Flo for ovulation predictions? Can it replace traditional methods?

Sometimes, ovulation symptoms (not period symptoms) give Flo more markers to figure out how your cycle goes.

Flo app accuracy for ovulation predictions explained on a graph

The graphics above show that the predictors that help increase Flo app accuracy are most often noticed during ovulation and during PMS.

It’s a well-known fact that the luteal phase is more stable than the follicular. Thus, if Flo knows when you finished ovulating, it makes better cycle predictions. The same is true for PMS: its indicators become noticeable in the luteal phase roughly at the same time each cycle. 

Considering all the available ovulation prediction methods, we see Flo more as your go-to virtual assistant to use alongside other means. Its predictions cannot be always considered 100% precise, but you can, for instance, save quite a lot of money on ovulation kits by using them only around the days Flo suggests you’re the most fertile. Or you can measure your BBT every day and log it in the app to see a comprehensive chart and improve digital predictions even more. 

If you’re trying to predict ovulation to avoid pregnancy, using a reliable form of birth control is still the best option for you.

How YOU can improve Flo app accuracy

As we mentioned above, Flo uses artificial intelligence to make more accurate cycle predictions. But no AI can learn your body patterns just from the basic info like your age or the dates of your previous periods. That’s why we gave you the ability to log symptoms.

Your mood swings, activities, physical indications — try to log as many of these as you can. The more data our AI has to process and analyze, the higher Flo app accuracy will become. Don’t be afraid to make Flo work harder for you — it can handle it :)

Final verdict: is Flo app accurate?

We should admit that apps are already smarter than us. Flo, for instance, uses machine learning: it takes your data and learns from it, reliably predicting ovulation and menstruation. The more you use the app, the higher Flo prediction accuracy becomes. 

Flo also has other advantages over traditional calendar methods and standard apps. You can track your overall feeling, symptoms, sex drive, menstruation flow — and the app will give you personalized health insights depending on the state of your body. If you’re looking for maximum precision in catching your fertile window, we still encourage you to measure BBT and use ovulation tests. With that said, Flo is a great virtual assistant and a real money-saver in this regard.

As our research has shown, thanks to using AI-based algorithms Flo is quite accurate in its predictions as far as period tracking apps are considered. Its efficiency is backed by numbers. So, thank you for choosing us! And if you haven’t tried Flo yet, get on board! 

Download Flo now and enjoy accurate cycle predictions, plus relevant information and educational content from health experts.

#1 mobile product for women’s health

You will receive a one-time SMS. We will not store or use your phone number in any other way.