Use this menstrual cycle calculator to calculate your next menstrual period, fertile period and due date. To give you an estimate please provide the requested information and press the Calculate button (results will be shown below, together with a fertility calendar):


When did your last period start?


How many days did it last?


How long is your cycle?


Below are the results based on the information you provided:

Your next menstrual period is expected to start on

Your next most fertile period is from to

If you conceive within this timeframe, your estimated due date will be

Previous 2 MonthsNext 2 Months

  • Pre-Period
  • Period Days
  • Post-Period
  • Peak Ovulation

Please note that this is only an estimation of your menstrual cycle

If you want to stand the best chance of getting pregnant, then you need to know when you are ovulating. This is the time of the month that you are at your most fertile, and thus stand a greater chance of a sperm reaching the egg and fertilizing it.

However, one of the biggest problems people have is knowing how to calculate their next fertile period. This is where technology can come in handy. You can use tools such as a menstrual cycle calculator which should provide you with a rough estimate of when you are going to ovulate next.

But of course, a period calculator is not the same as talking to a healthcare professional, so this is just to aid you in coming up with the most accurate calculation as much as possible.

Let us discuss how these calculators work and how you can maximize their use to your advantage.

Menstrual Cycle Calculators vary in complexity. Some will ask you for information such as your average body temperature, as well as various other bits and pieces about what your body is currently going through.

These types of cycle calculators often give the most accurate results, but many people find that they are “over kill”, and the majority of the information that they ask for is not something that people will have to hand readily, especially months of data about the subject. Therefore many women use simpler period calculators, which still give fairly accurate results.

Using a Menstrual Cycle Calculator

The first thing that the period calculator will ask you is the date of your last period. Hopefully this should be information that almost any woman should be able to answer fairly easily. This will be the starting date of the last period and not the ending date.

If you are still confused on how to determine it correctly, the Day One (the first day that menstruation started) is the starting date of your period and it can last from three days only to as long as seven days.

There are women who suffer from period pains within the first few days and can be such a dreaded time for them. It is due to the hormones in a woman’s body which cause the womb to shed the lining actively from the previous menstrual cycle build-up. Knowing this can be a bit of a relief since the pain can be excruciating and worrisome for some women.

The next piece of information that you will be asked for is the average length of time between your periods. This is the “length of the menstrual cycle“. Of course, the human body does vary wildly here, and whilst some months there could be 30 days between your period, and others it could be as low as 25.

However, you are only after an average here. Do try to be as accurate as possible though as this will affect the results that you are given, and this, of course, will have a profound effect on what the calculator tells you is the ideal time to try for a child.

Finally, you will be given your results. Generally, you will be told the date of your next period, which should be fairly accurate. What you are going to be most concerned with is the next ovulation period. This will be the time that you are at your most fertile and therefore stand the best chance of getting pregnant.

How To Calculate Your Next Period & Ovulation Infographic

Understanding the Menstrual Cycle Properly

While you may already have a fair understanding of your own menstrual cycle, there are women who have cycle lengths that vary. Sometimes, your own cycle can be between 23 days only or it can reach 28 or 30 days the next.

When a variation in menstrual cycle length occurs, that usually happens during the time of the cycle before you ovulate. This is referred by professionals as the follicular phase. Most women’s ovulation period and their monthly period happen between 12 to 16 days which is referred to as the luteal phase.

Understanding Your Next Menstrual Cycle and Fertilization

If you are trying to get pregnant you need to understand how the menstrual cycle works. The process starts when the thick lining of your womb starts to break up due to the decrease in estrogen and progesterone levels. Without sufficient amount of these hormones, your body will shed the lining and it will start to prepare for your next menstrual cycle.

However, if the egg was successfully implanted into the womb’s lining, your body will produce human Chorionic Gonadotrophin (hCG) or pregnancy hormone right away. The body will continue to produce the required estrogen and progesterone hormones so that the womb lining will not be shed and the placenta can grow to maturity enough that it can support the pregnancy.

Using a Fertility Calendar

The period calculator above also comes with a menstrual cycle calendar. You can navigate through different months by clicking on the NEXT 2 MONTHS and PREVIOUS 2 MONTHS links. This allows you to plan and prepare for your fertile and menstrual periods in the upcoming months.

What you do need to remember though is that the information isn’t 100% accurate as it is impossible to predict the human body, so ideally you would want to start having sex a couple of days before this. You can learn more about the likelihood of conception in this article.

Whilst they aren’t 100% accurate, the menstrual calculator is still a useful tool. It provides a “free” way of knowing when you stand the best chance of getting pregnant, and this of course can be a god send for a couple who is struggling to conceive a child.

Learn more

Want to learn more about your menstrual cycle? Find out how does the Fertility Calculator work or how to to calculate your period manually.

Want to know if you’re pregnant? Take this online pregnancy test, read more about the most common reasons why your period might be late or find out when it’s the best time to take a home pregnancy test.

Do you have a question about your period, ovulation, pregnancy or any other related topic? Check out our Frequently Asked Questions page.

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