Accurate Period Calculator私密的月经周期追踪工具，预测经期与排卵窗口期。

Am I late for my period?

A period is generally considered "late" if it hasn't arrived within five days of your expected start date, according to the American College of Obstetricians and Gynecologists (ACOG). However, since few people have a perfectly rhythmic 28-day cycle, it's normal to see slight fluctuations of 2-7 days. If you are sexually active and your period is even one day late, the most reliable next step is a pregnancy test, as our Period Calculator provides an estimate based on averages, not biological certainty. Source: ACOG Guidelines.

Asked by Quoc Bui · May 10, 2026

How do I calculate my next period date?

To find your next start date, you first need to identify "Day 1" of your last cycle. This is the very first day you noticed a steady flow. From there, add your average cycle length, which is the number of days from the start of one period to the start of the next. For example, if your last period began on March 1 and your average cycle is 28 days, your next period is predicted to start on March 29. According to NHS UK, most menstrual cycles range from 21 to 35 days.

Asked by Frank Müller · Apr 28, 2026

How do I calculate my "safe period"?

The "safe period" refers to the days in your cycle when you are least likely to conceive, typically at the very beginning and very end of your cycle. To calculate this, you must first identify your ovulation window, which is usually 12 to 16 days before your next period, according to ACOG. However, it is important to remember that the "Calendar Method" is not 100% accurate. Sperm can survive inside the body for up to five days, making it risky to rely on a calculator alone for contraception. Source: ACOG and NHS UK.

Asked by George Papadakis · Apr 24, 2026

Why did my period come early this month?

It is quite common for a period to arrive a few days early. According to research published in Women's Health Issues, this usually happens because ovulation occurred sooner than usual. Common triggers for an early cycle include high levels of stress (35% of cases), significant changes in your sleep schedule, intense new exercise routines, or even recent travel. If your period is consistently early (more than 7 days) or accompanied by unusual pain, consulting a healthcare provider is recommended.

Asked by Mustafa Yilmaz · Apr 9, 2026

How much flow is normal during a period?

The average person loses between 30 ml and 80 ml of blood over the course of their entire period, about 2 to 5 tablespoons, according to ACOG. In practical terms, this means soaking through a pad or tampon every 3 to 4 hours. If you find yourself needing to change your protection every hour or noticing clots larger than a quarter, your flow may be considered heavy (menorrhagia), and you should seek medical advice. Source: American College of Obstetricians and Gynecologists.

Asked by Carlos Mendoza · Mar 31, 2026