How to calculate your period and calendar of the menstrual cycle?

It is very common for women to wonder when their period will arrive. It can be for various reasons, such as, to organize their activities according to their cycle, for a baby project, to equip themselves with disposable or reusable sanitary protection.... So how can we reliably calculate the arrival of our menstruation?



How to calculate the date of your period?

Knowing the day of your period is both trivial and requires knowledge of the different phases of the menstrual cycle! To anticipate the arrival of your menstrual bleeding, you must first establish the average length of your cycle.

Determining the length of your menstrual cycle

A menstrual cycle starts on the 1st day of menstruation and ends the day before the next period.
In a simple way, it is enough to subtract the date of the first day of your last period from the day before your next period. It is preferable to repeat the operation on your last 3 cycles to obtain the average duration of your menstrual cycles.

Define your period and pregnancy calendar

It can sometimes be difficult to keep track of your menstrual periods and especially to remember all these dates on the calendar! Each woman is different, can have short, long, regular, irregular cycles... It is therefore useful to note down the dates of your menstrual losses, ovulation or any other change each month in a small notebook or paper menstrual calendar if you want to follow the occurrence of your monthly losses closely! Your general practitioner, gynecologist or health professional can also use an obstetric roulette to calculate this information in the context of a pregnancy!

Use a period application

A very practical method within reach of your smartphone is to use a period app to automatically track your period calendar and the day of your upcoming uterine bleeding and to better understand your symptoms throughout your cycle. There are plenty of menstrual apps on the market, it's up to you to choose the one that suits you best or to read our comparison! They all have their own specificities and some of them even go beyond the simple tracking of your period, offering features such as pill reminder,ovulation date, body temperature, ovulation calendar or pregnancy calendar... They all work on the same principle though: you just have to answer a few questions about yourself and your previous cycles.

Is it possible to calculate your period with an irregular cycle?

As we have seen, the menstrual cycle is calculated by subtracting the date of the day before the last period from the beginning of the previous one. But then, how to calculate its menstrual calendar when our cycle is particularly irregular and unpredictable?
For that, it is necessary to understand how the female cycle is divided. It is divided into three stages:

  • The follicular phase (before the release of the egg), lasts about 13 days
  • The ovulatory phase (release of the egg), lasts about 24 hours
  • The luteal phase (after the release), lasts about 14 days

On a classical cycle of 28 days, ovulation arrives on the 14th day, dividing the menstrual cycle in two. But in the case of a longer, shorter or irregular cycle, it is in fact the follicular phase that will last more or less time, the luteal phase does not vary, it lasts on average 14 days.
Thus, to know the day of your next menstrual flow when you have an irregular cycle, it can be useful to know how to spot your ovulation signs. You will then only need to add 14 days to this date to know your next menstrual flow.
The signs that indicate the approach of the ovulation period are the following:

  • Increase in your body temperature
  • Increased production of cervical mucus, with the texture of egg white
  • Stimulated sexual desire
  • Painful breasts or lower abdomen

All you have to do is pay attention to these symptoms and listen to your body to find your place in the cycle. Or use an ovulation test to confirm it! In the meantime, to prevent you from unpleasant surprises, you can wear menstrual panties as the fateful date approaches to be prepared for any eventuality.

When does ovulation occur during the menstrual cycle?

As we saw earlier, the female rhythm is made up of 3 phases, with ovulation generally occurring on the 14th day. This period corresponds to the moment when the ovary expels an egg and lasts only 16 to 32 hours. During sexual intercourse, the oocyte fuses with a spermatozoon and becomes an ovum, then a few days later an embryo that will nestle in the endometrium, the famous uterine wall. In the absence of fertilization, the uterus eliminates this mucous membrane, which causes the monthly blood loss.

For women who do not have a 28-day cycle, it is possible to know a posteriori their ovulation period by subtracting 14 days from the date of their last period. If an unprotected intercourse took place during this period, then it is possible that you are pregnant. You can then approach your health care professional for advice.

Is it possible to ovulate twice during the same cycle?

Although very rare, it is possible for both ovaries to produce an egg at the same time during the ovulation period. This is what gives rise to fraternal twins!
Be careful, however, this double ovulation is simultaneous and only occurs during the same window of opportunity, at the time of the ovulation period, which lasts about 16 to 32 hours. It is therefore not possible to have an ovulation on the 14th day of the cycle and a second ovulation several days later. If there can be a double ovulation, there is only oneovulatory phase per cycle!

Is it possible to get pregnant outside the ovulation period?

To put it simply: Yes, you must differentiate between the ovulation phase and your fertile period! Indeed, if ovulation only lasts 16 to 32 hours, theoocyte survives between 12 to 48 hours after its expulsion. Spermatozoa can survive up to 4 days in the body! It is therefore possible to have fertilizing intercourse a few days before or after the ovulation period itself, thus affecting the fertility window. Fertilization will then take place at the moment when the egg and the spermatozoon meet!

How does pregnancy affect the calculation of menstruation?

Pregnancy can impact the calculation of menstrual periods in two ways, which we will review.

At the beginning of the pregnancy

You have just become pregnant and in this case you observe a delay in your period. Pregnancy suppresses the menstrual flow because the endometrium becomes a soft nest in which the embryo implants. There is therefore no evacuation of the uterine lining and therefore no menstruation. A delay of more than a few days in your period should therefore alert you that a potential pregnancy has begun, especially if your cycle is regular!

After delivery

You have just given birth and in this case your period will not return until after you are back from childbirth. Right after the baby is born, you expel placental remains and other blood debris related to the pregnancy, the lochia, which can last 6 to 8 weeks. Then, the first post-delivery menstrual period can take place from 3 months to 18 months and more depending on whether or not you have been breastfeeding for a long time. These first periods are called the return of childbirth. The cycle will regularize itself afterwards to find your initial natural rhythm.


FAQ to calculate your period date

How to calculate the arrival of your period?

To calculate the arrival of your menstrual periods, you need to know how long your average menstrual cycle lasts: simply subtract the date of the day before your last period from the first day of your last period. Then add this number to the day of your last period to know thearrival of the next one!

How to know the date of my next period ?

You can calculate the arrival of your next period by hand or via an application. If you listen to your body, the symptoms of premenstrual syndrome will be able to guide you on the arrival of your menstrual losses (hormonal acne, chest pain, mood swings, cramps in the lower abdomen ...)

Does my period always come on the same date?

It is very variable and depends on each woman's cycle! Some women have a very regular cycle, while others have an irregular one. Stress, contraception and other factors can also influence the appearance of the flow.

What are the dangerous days of the menstrual cycle?