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How long is the average period cycle?

How long does the average period cycle last?

When it comes to periods, no two cycles are the same. Your period is unique to you, because you are a unique human being. That being said, we do see some similarities from person to person, and we can use these similarities as a guide, to educate and raise awareness of certain topics and issues surrounding menstruation. So when we talk about the ‘average cycle’, please know that it’s ok to fall outside of this. There really is no ‘one size fits all’.

Disclaimer aside, let’s look at the ‘average period cycle’ and how long it generally is for most people.

How long should my period be?

As we always say, you know your flow best, so with this in mind, we put the question to Mr. Narenda Pisal, consultant gynaecologist at London Gynaecology. 

He told us,

“A typical menstrual cycle lasts for 28 days, but women can have quite a lot of variation. The normal gap between the first day of two consecutive cycles (also known as cycle length) can range between 21 and 42 days.”

21 and 42 days? That’s quite a variation! So how easy is it to keep a track of your cycle, and know what is normal for you?

Cycle tracking

Cycle tracking can be a really useful tool to help you understand your own menstrual cycle better- and there are loads of great apps out there to try. 

How long does the average period cycle last?

Our top three are: 

1. Flo: this app helps you to track your cycle, and also provides accurate and informative articles and tips from doctors and experts too. The app itself is really easy to use, which is a definite plus if you’re new to tracking.

2. Clue: we love this app because it allows you to track so much more than just your period- from mood, to how your skin is doing. It really does give you a wider insight into your cycle and how it affects your health from top to toe. A great one for those who love data! 

3. Wild: this app is brilliant for anyone who is active and wants to learn how to maximise their workouts, training with their cycle and not against it. A really good app for those who are determined to wake up and kick ass!

Most cycle tracking apps will ask you to log the start of your period, alongside any PMS symptoms that you’re experiencing, such as bloating, cramps or sleep disturbances. You’ll then be asked to log the end of your period, and after a few months you’ll have a good picture of what’s happening with your cycle. Once you have a few cycle’s worth of data, your app can then predict when your next period is due, and you’ll have a better idea of what to expect in terms of symptoms too.

Even if you track just the start and end of your cycle, it helps to have a clearer idea of when to expect your period, how long it should last in general, and when something isn’t quite right. If you track symptoms too, you’ll have a lot more insight and it could help you get a diagnosis a lot more quickly if something is wrong. 

And not forgetting that knowing when your period is due can be incredibly empowering too- you’ll have a better idea of when to make sure you have a pair of period pants in your bag, and when to dig out the Stretch Seamless to help you ride out the bloating too. Knowledge is power after all!

How many days should I have between periods? 

How long does the average period cycle last?

When you know how long your cycle normally is, you’ll have a good idea of how many days you usually have between periods too. Not sure yet? To help you figure it out, it helps to understand the stages of the menstrual cycle. 

There are four phases:

Menstruation- usually lasting between 4 and 7 days on average- although, again, this varies from person to person, and if you track your cycle you’ll know what’s normal for you. 

Follicular phase- takes place at the same time as menstruation, and lasts between 14- 21 days.

Ovulation- the shortest phase of your menstrual cycle, lasting for just a few hours as the egg is released from the ovary to travel down the fallopian tube.

Luteal phase- the final phase, lasting around 12-14 days.

Keep in mind that the average length of each phase is just that- average. But the order by which each phase of the cycle occurs will be the same for each person, even if the length varies by a few days. 

Why am I suddenly having shorter cycles?

Period turned up early this month? There are so many reasons why this could be happening. Mr. Pisal told us,

“The normal cycle length is 21-42 days. If your cycle is shorter than this, then it could be an episode of intermenstrual bleeding outside of your normal cycle. Within this range, a shorter cycle could be due to a number of factors affecting ovulation such as age, perimenopause, acute illness, long distance travel, stress, body mass index, contraception, breastfeeding as well as pregnancy.”

So let’s look at each potential cause a little more closely.


Perimenopause is the transition towards menopause, where the ovaries stop working and eventually your periods stop altogether. There are many symptoms related to perimenopause as the hormones fluctuate more erratically, and many people find that their cycles become a lot shorter than normal. It’s also common to skip periods, sometimes for a few months in a row, and when they do return the bleeding can be heavy and unpredictable too.

How long does the average period cycle last?

If you’re aged over 45 and you’re experiencing other symptoms of perimenopause, this could be why your cycles are suddenly changing in length. Speak to your doctor about potential treatments that can help to ease the transition for you.


Stress can play havoc with your cycle, and can cause you to  not only miss periods,  but to experience changes in cycle length too. Try to take steps to reduce stress wherever you can, because it really can have a serious negative impact on many areas of your life, and not just your cycle.

Weight gain/ loss

Losing or gaining weight quickly can affect your menstrual cycle too, and can cause irregular periods as your hormones are forced out of balance. If you’re losing weight, try to do it in a healthy and sustainable way- slow and steady is best. 

Likewise, if you’re gaining weight quickly, you might need to make some modifications to your diet to restore the balance in a healthy way too. Speak to your doctor for advice on the best way to do this. 


Illnesses can have a knock on effect on the menstrual cycle, and especially if your immune system is taking a battering. Studies such as this one found that our periods are affected by our immune system, so it makes sense that our cycle can be affected when we’re not well. 

Hormonal contraception

If you’re on hormonal contraception your doctor may have already told you about potential changes to your menstrual cycle. Make an appointment for further advice if these changes don’t settle down after a couple of months. 


Breastfeeding can affect your period and many women actually find that their cycle stops for a while as they’re feeding their baby. The hormones involved in milk production actually halt the menstrual cycle so that your body can focus on feeding your baby, but they can return even before your baby moves on to solid food. 

Why am I suddenly having longer cycles?

In the same way that many factors can play a role in shorter cycles, there can be many reasons why yous suddenly start to experience longer cycles too. If you find that your period is late, it’s important to first rule out pregnancy, and then look at other reasons why this might be happening, including:

How long does the average period cycle last?
  • Perimenopause
  • Birth control
  • Change of medication
  • Stress
  • Delayed ovulation- this can occur for a number reasons including stress, medication, thyroid issues, PCOS and breastfeeding.
  • Uterine fibroids- non-cancerous growths which appear in and around the uterus. Most experience these without symptoms, but in some cases periods can be heavier and last longer. Speak to your doctor about potential treatments.
  • Thyroid issues- hypothyroidism can cause changes to your cycle and in some cases can stop them altogether. Speak to your doctor about this, for advice on treatment suitable for you.
  • PCOS- a hormonal condition which affects the regularity of periods. Speak to your doctor about treatments available. 
  • Endometriosis- a condition where endometrial tissue grows in other parts of the body, such as the ovaries or fallopian tubes. Those affected experience heavy and painful periods, sometimes lasting a lot longer than ‘normal’.
  • Adenomyosis- a condition where the endometrial tissue grows into the muscular wall of the uterus. This can cause very painful periods.

Speak to your doctor for advice if you regularly experience longer cycles, and make a note of any other symptoms you notice too. 

When to see the doctor

It can be worrying if you don’t know what’s happening with your cycle. Dr. Shashi Prasad, a specialist in integrative women's health and bioidentical hormone balancing for the Marion Gluck Clinic told us,

“Some women may start to note a change in their periods. 

  • It may become shorter, i.e., bleeding every 2 weeks or less.
  • They may become longer than every 35 days.
  • Or there is significant variation in your cycle length, with more than 20 days difference between your longest and shortest cycle.
  • The flow might become very light, or you are bleeding for hardly a day.
  • Or periods become very heavy with flooding and clotting or lasting for more than 7 days. 
  • Sometimes women may notice bleeding in between periods or after sex.

If you are noting these changes then it’s important to speak to a doctor, especially if the changes are going on for more than 3 months.”

Related posts:

Stages of a Period 

What Happens During a Period?

Irregular Periods

Period Problems

What Causes a Missed Period?

How Many Days Between Periods?


What is an unhealthy menstrual cycle length?

If you track your cycle, you’ll have a really good idea of what is normal for you. Cycle length can vary from person to person; if you’re concerned about how long yours is, speak to your GP for advice.

How long does the average menstrual cycle take?

The average menstrual cycle lasts around 28 days, but this can vary hugely from person to person. Anywhere from 21 to 42 days can be normal. Tracking your cycle can help you to understand what’s normal for you, so you can spot potential problems early on