When someone asks me if their app knows exactly when her period is do, my answer is usually…
“No, nope, still no, and hell no!”
That app doesn’t KNOW anything unless you give it A LOT of valuable information first. Information that goes way beyond inputting the day of your last period.
Most fertility apps base their “period-due-date” on estimates of when your last period was and how long the average menstrual cycle is. This is called the “calendar method” and uses population averages that are often outdated.
But you are not average, and your cycles aren’t either!
So unless you track AND confirm ovulation, an app can’t really predict when you can expect your period.
Here are some useful methods to TRACK ovulation:
➖ Ovulation predictor kits (OPKs)
➖ Cervical mucus
And some useful ways to CONFIRM ovulation:
➖ Your basal body temperature (BBT)
➖ Progesterone test strips
If you just started tracking and you have no idea when you can expect your period, keep in mind that on average, your period will show up 10-15 days after the day you ovulated. The time between ovulation and the start of your next period is called the luteal phase. And it’s usually steady from one cycle to the next.
So if your luteal phase is always ~11 days long, you are “late” when you’re 12 days past ovulation (DPO). If your luteal phase is usually 13 days, you are “late” when you’re 14 DPO.
The app you just installed won’t know any of that (yet). So keep that in mind and don’t rely too much on things like predicted dates!
If you want to try tracking your cycle, look for an app where you can input more than just dates (for example, Fertility Friend (iPhone / Android). You want one where you can also record things like your basal body temperature, your cervical mucus scores, if your OPKs were positive, and other signs and symptoms of ovulation that are relevant to YOU!