You can use this period calculator to calculate your next menstrual period, fertile period (best time to have intercourse if you’re trying to get pregnant), and due date. To give you an estimate as to when those time frames are, 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
- Pre-Period
- Period Days
- Post-Period
- Peak Ovulation
Please note that this is only an estimation of your menstrual cycle
Table of Content
- How Do Menstrual Cycle Calculators Work?
- Using a Period Calculator
- How To Calculate Your Next Period & Ovulation Infographic
- Understanding the Menstrual Cycle Properly
- Understanding Your Next Menstrual Cycle and Fertilization.
- Some Important Information Regarding the Calculator
- Learn more
- FAQ
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, during ovulation (which happens around day 14 of your cycle [1]) and is when there is a greater chance of a sperm reaching the egg and fertilizing it.
However, one of the biggest problems and questions that people have is knowing how to calculate their next fertile period and when is the best time to try. This is where technology can come in handy.
You can use these tools, such as a menstrual cycle calculator, can help 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 possible.
How Do Menstrual Cycle Calculators Work?
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.
While there are women who measure their basal body temperature, it’s not something that the everyday woman uses.
However, it is a rather accurate way (when done 100% correctly) to determine when a woman is ovulating.
Some feel that these types of cycle calculators are “overkill”, but for those who are using the basal body temperature to prevent and plan a pregnancy, they have this information handy.
If you aren’t into this type of strict monitoring, a simple calculator like the one provided here can give you really good results and help you plan.
Using a Period Calculator
The first thing that the period calculator will ask you is the date of your last period. With so many apps available now, this should be information that is readily available.
And just remember, when calculating your period, you use the first day of your last period. This was the beginning of your cycle.
If you don’t know the exact first day, calculate back from the last day however long it lasted, and start tracking now. Especially if you are trying to get pregnant.
Some will use a menstruation calculator to figure out when to expect their periods and when to expect PMS. PMS is due to the change in hormones that cause periods and pregnancy.
When you are pregnant or during your period, these emotional and physical symptoms subside [2]. Some women can then plan to change their diet a few days before they expect PMS and help to alleviate some of the symptoms.
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, others it could be as low as 25.
However, you are only after an average here. Being as accurate as possible is important as this will affect the results that you are given which can have a profound effect on when the calculator tells you is the ideal time to try for a child.
Finally, you will be given your results. Based on the information you provided, it will calculate when your next period is anticipated and also your fertile period which is when you stand the best chance to get 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 as short as 23 days on cycle and 28 or 30 days the next.
When a variation in menstrual cycle length occurs, it usually happens before you ovulate. This is referred to as the follicular phase which encompasses menstruation as well and ends when you ovulate [3]. A woman generally ovulates between days 12-16 of their cycle which is the start of the luteal phase [4].
There is a multitude of reasons as to why your period could be altered, be it stress or medications, even weight gain/loss or travel. Unless you think you are pregnant, it could be a myriad of reasons that have your period coming irregularly.
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 a sufficient amount of these hormones, your body will shed the lining and it will start to prepare for your next menstrual cycle.
However, if a sperm does make contact with and fertilizes the egg, it will close off to prevent more from getting in there. It will stay in the fallopian tube for 3-4 days then move to the uterus and attach to the wall, staying there for the long haul of pregnancy.
Your body will produce human Chorionic Gonadotrophin (hCG) or pregnancy hormone right away (which can immediately be seen by a blood test and can take about 2 weeks if not longer to be seen in urine tests) [5].
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 mature enough that it can support the pregnancy.
Some Important Information Regarding the Calculator
The period calculator above also comes with a fertility 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.
Your fertile period gives you a good range in when to have intercourse to potentially get pregnant. You can learn more about the likelihood of conception in this article.
That being said, the menstrual calculator is still an extremely useful tool. It provides a simple way of knowing when to anticipate your next period and when is the best time to try for getting pregnant.
This could be a huge help for those with busy schedules to plan their days to start their family.
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.
FAQ How do I calculate the length of my cycle? From the first day of your last period to the first day of your next period. That would be the length of your cycle.
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Can I have sex during my period? While it’s messy, some women are more turned on during their periods. Throw down a towel and have fun. It can ease cramps and PMS symptoms and even shorten the duration of the period [6]. While all sound like great things to me.
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What is “average” for periods? Average depends on the person, but the most reported facts about your period are that they last generally from 3-8 days [7]. Everything else is based on the person, whether they get PMS symptoms such as bloating and cramping, and how heavy the flow is. This can also be dependent on birth control usage.
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My period is really heavy; what can I do to change that? Many women take birth control to regulate their periods. The benefits of this would be to potentially stop ovulation, change the lining of the uterus as well as changing the cervical mucus. This can result in lighter, more regular and even nonexistent periods [8] (some women don’t get a period while on birth control, with the exception of Paragard users which is non-hormonal). It can also help relieves PMS symptoms and acne too all while preventing pregnancy.
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Can I get pregnant if my periods are irregular? Yes, but it makes calculating ovulation a bit harder with only a calculator. Ovulation tests might be more helpful.
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How do I know if I need to see a doctor? If you are going through more than 10 pads or tampons per day or soaking through one an hour, then it’s time to talk to your doctor about it [9]
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Can I prevent PMS? If your body is made for PMS then generally not get rid of it completely, however, hormonal birth controls can help, as well as cutting back caffeine and salty foods and increasing exercise before your period may help [10]
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From the first day of your last period to the first day of your next period. That would be the length of your cycle.
While it’s messy, some women are more turned on during their periods. Throw down a towel and have fun. It can ease cramps and PMS symptoms and even shorten the duration of the period [6]. While all sound like great things to me.
Average depends on the person, but the most reported facts about your period are that they last generally from 3-8 days [7]. Everything else is based on the person, whether they get PMS symptoms such as bloating and cramping, and how heavy the flow is. This can also be dependent on birth control usage.
Many women take birth control to regulate their periods. The benefits of this would be to potentially stop ovulation, change the lining of the uterus as well as changing the cervical mucus. This can result in lighter, more regular and even nonexistent periods [8] (some women don’t get a period while on birth control, with the exception of Paragard users which is non-hormonal). It can also help relieves PMS symptoms and acne too all while preventing pregnancy.
Yes, but it makes calculating ovulation a bit harder with only a calculator. Ovulation tests might be more helpful.
If you are going through more than 10 pads or tampons per day or soaking through one an hour, then it’s time to talk to your doctor about it [9]
If your body is made for PMS then generally not get rid of it completely, however, hormonal birth controls can help, as well as cutting back caffeine and salty foods and increasing exercise before your period may help [10]
Do you have any other question about your period, ovulation, pregnancy or other related topics? Check out our Frequently Asked Questions page.
References
- Your Fertility. Women’s Guide to Getting the Timing Right [link]
- Mayo Clinic. Premenstrual Syndrome (PMS). [link]
- Better Health Channel. Menstrual Cycle. [link]
- see above #3
- WebMD. Pregnancy and Conception. [link]
- Eleanor Jones via Cosmopolitan. 10 Questions Period All Guys Want Answered [link]
- Playtex. Period 101. [link]
- The University of Iowa. Birth Control Pill Fact Sheet. [link]
- WebMD. Slideshow: Answers to Your Top period Questions. [link]
- see above #9
My last period was at 08/26 then I had unprotected sex at 09/14-09/15 and 09/17 then begain my pre-period light bleeding colour light red n Brown 2days 09/25-09/26 is it still save or am I pregnant?
Hi Maggie, have you taken a pregnancy test? If your last period was 8/26 then you are a bit late for your next period.
I saw my period on 28 of September and finished on 1st of October ,had unprotected sex on 4th of October..and started menstruating again on October 9th it’s normal or my pregnant
Hi Judith, that would be around the time of ovulation so that could be ovulation spotting/bleeding. That should have only lasted roughly three days at most and wouldn’t have been as heavy as your regular period. You shouldn’t have been in your fertile period until roughly the 8th which is why I would connect the bleeding to ovulation. You should anticipate your next period somewhere around the 26th of this month.
I had my last period from 10 of September to 13 of September now on the 6 of October,am bleeding again, could this be my usual period or implantation bleeding?
Hi Becky, If it’s lighter than your regular period it could be implantation, however, getting your period within the 25 day range is reasonable and nothing to be worried about. It could be your regular period.
I had my period on 30 august but it two days heavy but rest 3 day didn’t come much and had it on 22 September and that one lasted for 5 days and also have unprotected sex on 5 day of period could i conceive
Hi Anifa, It’s normal to have a shorter cycle. I would say on the 5th day of the period you wouldn’t generally be able to get pregnancy however, if your cycle is really short you might be able to get pregnant at the end of your cycle. However it’s not likely.
I had my period on 9th Spt-14 had sex on Spt 29,30 and 1st of October 2 and 4th of October
What’s the chance of me getting pregnant
Hi Ras, your fertile period would have been the 19th to the 23rd of September. So it doesn’t seem likely that you would have gotten pregnant. You should be expecting your period within the next day or so as well. If you don’t get it I would take a pregnancy test.
Hi my last period was 15th of september and i had sex with my boyfriend last 25th of september after 2 days i had a very light spotting, am i pregnant?
Hi Shey, two days later wouldn’t be implantation bleeding, that is far too soon. However, the 25th was within your fertile period so you could have gotten pregnant. I would wait until your next anticipated period which would be around the 13th of October before taking a test however if you think you might be.
1st day of my last was period 8/17, had unprotected sex on 8/30-8/31, began my pre-period/spotted 9/9-9/10 bleed for 1 day & ended. Should I be concerned or what are my chances of being pregnant?
Hello Meme, yes you might have conceived.