There are many reasons why women often like to track their menstrual cycles. Some like to find out when they’re ovulating so they can have sexual intercourse at the perfect time to conceive, whereas others specifically track their cycles to prevent conception. You may simply want to know when to expect your period so you’re not taken by surprise. Whatever your reason, there are a host of ways you can work out where you’re at in your cycle and when your next period is due.
How to calculate your next menstrual cycle
Below, you can find the easiest ways to calculate when your next period is due. You can do this by working it out yourself or using an app to do the work for you.
Work it out yourself
You can work out when your next period is due or when you are ovulating by doing some basic period maths.
The first day of a menstrual cycle is the first day of your period, and the last day is the day before the bleeding starts. The average time between these two events is 28 days, but each woman is different and this time period can be shorter or longer. For most women, it falls between 25 and 30 days.
For many women, the length of their actual period can differ too. Most will experience bleeding for an average of five days, though it’s common for bleeding to last anywhere between three and seven days.
It’s also worth noting that your menstrual cycle likely won’t be exactly the same length each month - some months it may be longer or shorter than others, and this is very normal.
To work out when your next period will be, you should take note of the first day of your last period and add 28 days. This will give you an approximate date of when your next period will start.
If you want to be a bit more specific than this, you can track the data over three months and find an average cycle length. For each month, make a log of when your period started and then count the number of days between then and your next period. After three months, you will have three numbers (such as 25, 30 and 28). Add these together and divide them by three to get a more accurate average. In this example, the average cycle length over three months would be 27.6 days.
Use an app
It seems that there is an app for every eventuality these days, including to track your period. This can be particularly useful as you can see approximately when your period is due many months in advance, something that comes in handy should you wish to delay your period for a certain event or holiday.
Each app is different and has a variety of features, some that you might want and others that you might not care about. The most popular cycle tracking apps in the UK include Clue, Eve, Flo, FitrWoman, Glow and Period Plus. Many of these apps are multifunctional and can track ovulation (though this may not be an appropriate method of contraception), as well as your period, and some allow you to track certain symptoms so the app can ‘learn’ more about you.
These apps work by initially tracking your period as if you were an average woman with a period length of five days and a cycle length of 28 days. However, the longer you input data for and the more information the apps gain about you, the more accurate they can become.
Can your menstrual cycle change?
The timing of your menstrual cycle can be affected by a lot of external factors, which is why it might not always come at exactly the same time each month. While this can be frustrating, particularly when you’re trying to track your period and it comes when you’re not expecting it, it’s absolutely normal.
Things that can change the dates or timing of your menstrual cycle include stress, polycystic ovary syndrome (PCOS), endometriosis, your weight (being underweight or overweight), excessive exercise, perimenopause and breastfeeding.
Occasional irregular periods are fairly common and a person is considered to be having irregular periods if their cycle is longer than 38 days or if the length of each cycle varies by more than seven days (for instance, the cycle is 25 days one month and 33 days the next).
A progestogen-only pill, such as Lovima®, works by preventing ovulation, meaning you’re less likely to have a period each month. Other forms of contraception that could have the same effect include the implant and IUDs (coil).