Period Calculator

Take the first day of your last period and add your average cycle length — that's your estimated next period date. So if your period started on March 1 and your cycle is 28 days, you'd expect your next period around March 29. The tricky part is knowing your actual cycle length, which is why tracking for a few months helps. Count from day 1 of one period to day 1 of the next — that's one full cycle.

A normal menstrual cycle is anywhere from 21 to 35 days, with 28 days being the most commonly cited average. But here's the thing — only about 13% of people actually have a perfect 28-day cycle. Most people fall somewhere between 24 and 32 days, and it's completely normal for your cycle to vary by a few days from month to month. A variation of up to 7-9 days between your shortest and longest cycle is still considered regular.

A late period doesn't always mean pregnancy — there are a bunch of reasons your cycle might shift. Stress is a big one, since cortisol can directly delay ovulation. Other common causes include significant weight changes, starting or stopping birth control, illness, travel across time zones, over-exercising, thyroid issues, and PCOS. If your period is more than a week late and you're sexually active, it's worth taking a pregnancy test. If you're consistently late or skipping periods, check in with your doctor.

Absolutely — and it's not just in your head. When you're stressed, your body produces more cortisol, which can suppress GnRH (the hormone that kicks off your whole cycle). This can delay or even prevent ovulation, which pushes your period back. Acute stress (like a big exam or a move) might delay your period by a few days to a week. Chronic stress can cause more significant disruptions, including skipped periods entirely. This is your body's way of saying "now isn't a great time for reproduction."

Most periods last between 3 and 7 days, with 5 days being the average. The heaviest flow is usually on days 1-2, then it gradually tapers off. If your period consistently lasts longer than 7 days, involves soaking through a pad or tampon every hour for several hours, or includes clots larger than a quarter — that's worth mentioning to your doctor. On the flip side, very light periods (1-2 days) can be totally normal for some people, especially on hormonal birth control.

It depends on how irregular we're talking. Cycles that vary by a few days each month? Totally normal — your body isn't a clock. But if your cycles swing by more than 9 days (say, 24 days one month and 38 the next), or you're regularly skipping periods, it's a good idea to talk to your doctor. Irregular periods can sometimes signal conditions like PCOS, thyroid disorders, or hormonal imbalances that are very treatable once identified. Also worth noting: periods are often irregular during the first few years after starting, after stopping birth control, and during perimenopause.