COVID-19 Information

Is Your Ovulation Calculator Lying to You?

Written By: Dr. Victoria Snegovskikh on January 31, 2017


Few would argue with the notion that the smartphone has had a tremendous impact on the way we approach our personal health and well-being. With little effort on my part, my phone will estimate how many steps I’ve taken in a given day, how many floors I’ve climbed – it even attempts to analyze the quality of my sleep!

A study published by the Pew Research Center reported that mobile apps that track a woman’s menstrual cycle were the fourth most popular health app downloaded by adults. (Click here to download a copy of the report.) This data is certainly supported by my own experience, as the majority of my patients who are trying to get pregnant are using some form of a smartphone menstrual cycle tracker, and most of these have a built-in ovulation calculator.

Now, I don’t discourage my patients from using these apps – in fact, they can be very helpful! Strategically timing intercourse so that it occurs just before and during ovulation gives a couple the best odds of getting pregnant.

But you do have to wade through a sea of inaccurate and poorly-built apps in order to find the few that really work well. Fortunately, a new study has done that for you, and I’m listing the top five apps below.

Not all ovulation calculator apps are created equal

Last year, a comprehensive research study published in the medical journal Obstetrics & Gynecology set out to objectively evaluate and rank 108 free smartphone menstrual cycle tracking apps. Rankings were based on accuracy, security and whether or not medical research was cited in development. Apps also scored higher if they were easy to navigate, could be used offline, and were free of advertisements and in-app purchases.

The study’s findings were disconcerting, if not slightly alarming. Out of the 108 free apps in the study, only 20 – less than 1 in 5 – were identified as being able to accurately track a woman’s monthly cycle. Of the 88 apps deemed inaccurate, many contained misleading or outright false health information. Plus, out of all the apps only one – an app called Clue – cited medical literature to back up its data.

The top five apps identified by the study were Clue, Day After, FemCal Lite, Fertility Cycle and The Flow. Since this study was published, I’ve been recommending that my patients use Clue. It’s relatively accurate, it’s easy to use, and it’s available for both Apple and Android devices.

Many apps can’t handle most women’s irregular menstrual cycles

I consistently have to remind my patients that only around 15 percent of women have a “regular” 28-day cycle. Most women fall somewhere along a range of 21 to 35 days, and it can vary a bit month to month.

Some of the apps evaluated in the study mentioned above simply defaulted to a 28-day cycle. While this number represents the “average” cycle, you can see just how wrong it might be if a woman’s cycle falls on either end of the 21 to 35-day range.

For this reason, you want to select an ovulation calculator app that allows you to input data from your previous cycles. Once a few months’ worth of data is entered, the app will start predicting the ovulation with a fairly high degree of accuracy.

Before that data is recorded, the ovulation calculator may be off by several days. Any woman who is trying to get pregnant and notes that her cycle regularly falls outside of the 21 to 35-day range is advised to make an appointment with a fertility specialist.

Smartphone ovulation calculators will never be perfect

As you can see, once we weed out the bad apple apps, only a handful remain. If you’re going to use an app to track your cycle and ovulation, which is certainly okay to do, it’s important to be picky and discerning. It’s also important to remember that no app will be 100 percent accurate in predicting what the human body will do.

As a side note, you may find it helpful to use an at-home fertility test in conjunction with your smartphone app. I discussed these in detail in a previous blog post. They have their own set of tips and precautions, so please read that post if you’re interested in going that route.

Lastly, if you’ve been trying to get pregnant for 12 months or more with no success (or six months or more if you’re over age 35), I encourage you to schedule an appointment with a fertility doctor. A trained reproductive endocrinologist can identify infertility issues you or your partner may have a lot better than any app can. After an initial work-up, the doctor will review your available treatment options.