Period Tracker

Once upon a time people used the stars for navigation and thought the earth was flat. We’re better than that now. Thanks to modern science (namely period trackers), knowing exactly when to throw an extra Tampax or two into your bag doesn’t have to be a complete shot in the dark anymore. Simply punch your info into our period cycle tracker to see when you might be feeling that PMS bloat, when you can expect your period, and when you’re the most fertile during ovulation.

1. When did your last period start?
2. How many days did your period last?
3. How long is your menstrual cycle?

Please note that this is an assessment of your menstrual cycle only.

There’s nothing worse than feeling a little squish in your pants and being faced with the potential horror that you might’ve just started your period unprepared. “When should I get my period?” you wonder, followed by “Did I just start my period?” are not the best things to cross your mind on a day you’re not expecting it. Be your own period prepper with the Tampax Period Calculator to know when your flow is about to start. For those vagina-havers with regular cycles (how’s it feel to be genetically lucky?), use our period calendar tracking tool to find out when you can roll the dice with your favorite pair of white jeans.

How do menstrual calculators work? Glad you asked. Basically, your body runs on a four-part “menstrual cycle” — and while you might assume that phrase means just the week of bleeding, in actuality, your menstrual cycle also refers to the weeks you don’t bleed. Your body is still grinding and putting in work — it’s not like your reproductive system just goes all-out the one week you bleed. You start with the menstrual cycle (your period, when the lining of your uterus sheds), followed by the follicular phase (when the follicles in your ovaries mature and get ready for the prime time: ovulation), then comes (you guessed it) ovulation (when the egg is released), followed finally by the luteal phase (when the egg makes its way down your fallopian tubes and gets ready to bleed).

Knowing this, you can track your period and your cycle. Voila!

It’s like those annoying SAT logic questions. If luteinizing is def gonna happen, then the menstrual cycle is def gonna happen next, and it’s only a matter of time before you bleed. You can also tell other ways to see where in your cycle your body is, like tracking your basal body temp (your temp when you first wake up), and checking your cervical mucus, both of which are helpful to know if you want to see if you’re ovulating, aka at your most fertile. But since seeing your period is an easier way of pinning down where you are in your cycle, tracking the days you bleed can also help you fill in the missing gaps to better picture your cycle’s timeline.

It’s using this information that you can get a chronological, clearer picture of what to expect.

Of course, not everyone’s cycle is totally the same. The average length that people usually go by is 28 days, but anywhere from 21 to 35 days is normal too, so don’t stress if you tend to be on the earlier or later side, as long as it’s consistent for your bod. If you’re on birth control, this can also help give you a more stable idea of your cycle, as birth control regulates your period a bit better.

But whether your period is three days, five, or seven days, whether it comes every month or more like every month-ish, you can still use a period calculator to better learn your cycle. How to Use a Period Tracker: Simply input the length of your average period and the length of your last period, and let the period calculator do the rest.

Pop in the date your last period began, the length of time it lasted, and the average length of your cycle to get a better idea of when you can reasonably expect your next period. If you have no idea how long between your periods, make a note the next time it starts and when it ends so you have it on hand for next month. Better late than never amirite?

You can also use a “period tracker” for way more than just predicting bleed week. Since ovulation usually occurs on the 14th day of your cycle (with Day 1 of your cycle being the first day you bleed), you can also learn and track peak ovulation.