How To Calculate Safe Period To Avoid Pregnancy?



Sex gives natural pleasure. But it comes with a baggage called pregnancy. Children are a blessing for those who are ready to expand their family. However, not every adult having an active sex life would want a baby. Would they? While there are several birth control measures you can follow, it is imperative to make your safe days calculation in order to avoid an unwanted pregnancy.

MomJunction tells you how to calculate safe days to prevent pregnancy, the various methods involved in it and more.

How To Calculate Safe Period Days

A menstrual cycle is calculated from the first day of your period to the first day of the next period (1). Safe period is from day 1 to 7 and day 21 to the rest of the cycle, when you can have sex without worrying about getting pregnant. This period will not be the same for all women as it depends on the length of the menstrual cycle. The average menstrual cycle is 28 days or a little less, but if your cycle is longer than 28 days, the safe period is not reliable.

It is important to have an understanding of the three stages of the menstrual cycle to avoid pregnancy.

Stages Of Menstrual Cycle:

Stages Of Menstrual Cycle

Image: Shutterstock

The length of the three stages of menstrual cycle differ from one woman to the other and also from cycle to cycle, but the average duration would be 28 days (2).

1. The Pre-Ovulatory or The Follicular Phase:

It occurs in between the days 2 and 14 when your body releases hormones that stimulate the eggs in the ovaries to grow. The hormones will also thicken the uterus lining to receive the fertilized egg. This phase is controlled by Estradiol hormone (3).

2. The Ovulation Phase:

It occurs in the middle of your menstrual cycle where a mature ovarian follicle opens up to release an egg for fertilization. It is the most sensitive phase where a woman has a great chance to become pregnant.

3. The Post Ovulatory Or Luteal Phase:

It is the last phase, which begins after ovulation and ends either in pregnancy or in the next menstrual cycle. In this phase, the uterus lining turns thicker prepare for pregnancy.

The luteal phase lasts from 10 to 16 days with the average being 14 days. But if it is less than 12 days, it is hard to become pregnant. The length of the phase varies from woman to woman but usually remain consistent from cycle to cycle.

The infertility period depends on the lifespans of both egg and sperm. In an average 28-day menstrual cycle, ovulation occurs on the 14th day. For women whose cycle is between 26 and 32 days, it could occur anytime between 12th and 19th day.

A sperm can remain alive for 3 to 5 days in the reproductive tract. Therefore, there is a high possibility to conceive if you have unsafe sex five days before ovulation time. The egg remains alive for only 24 hours, and if the fertilization does not occur within that time, it will die away.

Various Methods To Calculate Safe Period To Have Sex:

You need to be careful while calculating safe period because doing it on your fingers or in the air could lead to wrong results. Remember that you must avoid sex or use condoms, cap, diaphragm or other contraceptive methods during unsafe days.

Use these proven online calculating methods to know your safe days:

  1. Safe Period Calculator
  2. Fertility Awareness-Based Methods

1. Safe Period Calculator:

This calculator requires you to know your menstrual cycle changes so that you can determine the safe days to have sex. Know the safe period by entering the first day of your last period and the duration of your last menstrual cycle. It helps you find the safe and unsafe dates for having sex (4).

Safe Period Calculator

Your safe period

Mon Dec 04 2017 16:12:01 GMT-0800 (Pacific Standard Time) to Sun Dec 10 2017 16:12:01 GMT-0800 (Pacific Standard Time)
Sun Dec 24 2017 16:12:01 GMT-0800 (Pacific Standard Time) to Sat Dec 30 2017 16:12:01 GMT-0800 (Pacific Standard Time)

Who Can Use Safe Period Calculator?

You can use this method if the average length of your menstrual cycle from the past six months is between 26 and 32 days, and the variation between the shortest and longest cycles is seven days or less.

But before calculating your safe period, consult your doctor to understand the effectiveness of natural family planning methods. The expected failure rate of this method is about 3 to 4% per annum.

Who Cannot Use Safe Period Calculator?

  • You cannot use this method if the average length of your menstrual cycle is less than 26 days or more than 32 days, and the variation between the shortest and longest cycles in the last six months is eight days or more.
  • After childbirth, you can use this calculator only after six regular menstrual cycles.
  • Teens and women reaching menopause cannot rely on this method.

2. Fertility Awareness-Based Methods (FAM):

Fertility awareness, also known as natural family planning, is a way of predicting safe and unsafe days of your menstrual cycle. These methods are usually based on certain signs your body gives in response to the hormones that cause ovulation (5).

FAM are based on the below assumptions:

  • One egg is released in each cycle.
  • Egg lives up to 24 hours.
  • Sperm lives up to six days and can fertilize an egg during this period.
  • A woman will be fertile for almost six days before ovulation and two to three days after ovulation, so the total number of fertile days is seven to eight in each cycle.

How Do FAMs Work?

The FAMs work by alerting you on your ovulation days. Once you know your days of ovulation, you can avoid sex or use a contraceptive to keep the sperms away from the vagina.

It will help you know the unsafe days that come before and after ovulation. You can track the fertility pattern, marking the days when you are fertile and days you are not. You should do it carefully as the pattern changes from month to month.

Ovulation Predictors: You can also get test kits that help predict ovulation. They are very helpful in planning pregnancies. However, you cannot completely depend on them to avoid pregnancies.

Emergency Contraception: If you have unprotected intercourse on a fertile day, then use an emergency contraception. It helps prevent pregnancy if taken up to five days after unprotected sex. The earlier you take it, the better it works.

What Are The Different Fertility Awareness-Based Methods?

There are several FAMs to keep you away from unwanted pregnancy. They also assist you to track your fertility patterns when trying to conceive.

  1. Basal Body Temperature Method: It depends on your body temperature, which you need to track every day to know when you ovulate. There will be a rise in temperature during ovulation.
  1. Cervical Mucus Or Ovulation Method: It involves checking the changes in the cervical mucus every day in the first stage of menstrual cycle until you ovulate. The vaginal discharge changes when you ovulate.
  1. Calendar Or Rhythm Method: Here, you will chart your menstrual cycles on a calendar to predict ovulation based on the past cycles.
  1. Sympto-Thermal Method: This is the most efficient method since it is a combination of all the above. It involves basal body temperature, mucus, calendar methods along with tracking cervix changes, abdominal heaviness, breast tenderness, slight spotting and mild abdominal pain.
  1. Standard Days Method: If your menstrual cycle falls in between 26 and 32 days for a long time, this method works to record your monthly periods and determine your fertile days. Here, your unsafe days will be 8 to 19.

Let us understand all these methods in detail:

1. Basal Body Temperature (BBT) Method:

You will have low temperature in the initial phase of your menstrual cycle. It increases slightly after you start ovulating. The body temperature remains high for the remaining part of the cycle. It falls again before you start your next period. Tracking your temperature day by day will help you understand when you can ovulate. You should not have unprotected sex for three days after ovulation so as to avoid pregnancy (6).

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BBT is your body temperature when you are at rest. It differs from woman to woman but is usually between 96 and 98 degree Fahrenheit before ovulation and rises to 97 to 99 degree Fahrenheit after ovulation. Even if you find any deviations, they will be in fractions like 1/10 to ½ of a degree.

Use a unique large-scale thermometer, which can mark 96 to 100 degree Fahrenheit and is easier to read. You will get the basal thermometer in most drug stores for around $10. Rectal thermometers are more reliable than oral or any other types.

How To Check The Temperature:

Take Your Temperature:

Note your temperature every day in the morning before you get out of the bed. Make sure you do not talk, eat, drink, have intercourse or smoke before taking the temperature. Keep your thermometer for about five minutes and then note the reading.

Chart The Temperature Pattern:

Record the reading in a chart, which you can get from a women’s health center or your doctor. Over the days, you can observe a pattern in your temperature. The increase in the temperature may be gradual, sudden or intermittent. The pattern will differ from one cycle to another cycle.

The factors that may affect your pattern, i.e. your temperature are:

Being upset, having improper sleep, stress, illness, smoking, jet lag, drinking excessively or using an electric blanket. You should mark all these events on the chart to understand the pattern.
In the beginning, you may take the help of your doctor, family planning specialist or a nurse to read the graph. Make sure you chart at least three months before using this method to avoid pregnancy.

Chart The Temperature Pattern

Image: Shutterstock

Safe/Unfertile Days Using BBT Method:

The safe days are when the temperature is normal. The unsafe days start on the day the temperature rises and last for at least three days. They end once the temperature falls before your next period starts.

The Effectiveness Of BBT Method:
  • It is good at predicting when you can ovulate, but it cannot give you the exact day.
  • As the temperature does not rise until you begin to ovulate, you need to ensure that the sperm is not waiting in your body to mate with the egg. As mentioned earlier, sperm can be active for about five days in your body.
  • Combine BBT with any other FAM to be safe.

2. Cervical Mucus Or Ovulation Method:

The hormones which control menstrual cycle also stimulate the cervix to produce mucus. It usually gets collected in your cervix and vagina. It changes its amount and consistency just before and during ovulation. You can learn to recognize its changes so as to predict fertile and unfertile days. This method is also called the Billings method (7).

Here Is How You Do It:

Check Your Mucus Pattern:
  • While you menstruate, the flow covers the mucus.
  • After your menstruation, there will be no mucus production for a few days which are usually referred as ‘dry days.’ These are considered to be safe days if your cycle is longer.
  • When the egg begins to ripen, you will produce more mucus, which you can see at the vaginal opening. It will be white, yellow or cloudy and you can feel it to be sticky.
  • You will have more mucus just before you ovulate, and it looks clear and slippery. If you hold it between your fingers, it stretches. This property is known as Spinnbarkeit, a German word for fibrosity and stretchiness. This indicates your peak fertility days.
  • You will have about four days with slippery mucus, and then there will be a sudden fall in the flow. You will have a few dry days before your next period.
Chart The Mucus Pattern:

You can mark your mucus patterns on a calendar every day. Mark your period days, dry days, sticky days, wet days and slippery days. You can notice that your mucus will be different at every stage. You can understand it better if you have someone to help you learn the pattern.

Chart The Mucus Pattern

You Can Use Various Ways To Check The Mucus:
  • Wipe the vaginal opening with a dry tissue before urination. Check its texture and color.
  • Check the texture and color of the mucus on your panties.
  • Put a clean finger into your vagina and observe the texture and color.
The Factors That Affect Mucus Pattern Are:
  • Cervical surgery, if it is done with electrocautery or cryotherapy
  • Breastfeeding
  • Douches or other feminine hygiene products
  • Recent use of hormonal contraceptives or emergency contraception
  • Spermicides
  • Perimenopause
  • Vaginities (sexually transmitted diseases)
Safe/Unfertile Days Using Mucus Method:
  • If your cycles are short, your period days are not safe as the flow can cover your mucus.
  • In long cycles, the dry days after menses will be safe.
  • Safe days start after high slippery mucus decreases and becomes sticky again. The dry days that follow these are also safe.
  • Unsafe days start two to three days before you notice slippery mucus. They will remain for three days after slippery mucus increases.

You should abstain from unprotected sex for at least one full cycle before you understand this method completely.

The Two-Day Method:

It is also a mucus method which works best for those who are sure about their mucus secretions (8). Ask these two questions to yourself:

  • Did I secrete mucus today?
  • Did I secrete mucus yesterday?

If the answer is no, then it is a safe day for unprotected vaginal intercourse. Women who rely on this method will have 12 safe days for each cycle.

The Effectiveness Of Cervical Mucus Method:
  • For every 100 couples who use this method perfectly for one year, three women get pregnant.
  • For every 100 couples who use two-day mucus method for one year, four women get pregnant.
  • This method is not effective for those who do not produce mucus. Women who ovulate on day seven or eight will have petite mucus.

3. Calendar Or Rhythm Method:

You should maintain a record of the length of each menstrual cycle to know your fertile period. You can take an ordinary calendar and circle the first day of your period. Count the number of days present in each cycle, including the first day. Do it for eight to 12 continuous cycles (9).

Record Of Menstrual Cycles:
 Jan 10 29
 Feb 8 28
 Mar 7 29
 Apr 5 29
 May 4 26
 May 30 28
Jun 27 30
Jul 27 27

Do not use this method if most of the cycles are less than 27 days.

Chart The Calendar Pattern:

For predicting the first fertile day in your present cycle:

  • Check for the shortest cycle from the record.
  • Deduct18 from the total number of days.
  • Count that resultant number of days from the first day of your current cycle, and name the day as X.
  • This day X is your first fertile day.

For predicting the last fertile day in your present cycle:

  • Check for the longest cycle from the record.
  • Deduct 11 days from the total number of days.
  • Count that number of days from the first day of your present cycle, and name it as X.
  • This day X is your last fertile day.

This example may help you understand better:

To predict your first fertile day: Assume that your shortest cycle is 26 days, take off 18 from 26. It gives you eight. If the first day of your period is 1st, the day you name X is 8th. This would be the first day you are most likely to be fertile. You should abstain from unprotected sex from this day.

To predict your last fertile day: Assume that your longest cycle is 30 days, take off 11 from 30. It gives you 19. If the first day of your period is 1st, the day you name X is 19th. This would be your last day of fertility. So, you can indulge in unprotected sex after this day.

photo of the safe period chart

The Effectiveness Of Calendar Method:
  • It just predicts the most likely fertile days. Do not have unprotected sex in those days by any chance.
  • It is risky if your cycles keep varying in length. Therefore, you should always use this with other fertility awareness methods.

Some people use rhythm method with a pull-out or withdrawal. However, you should avoid it especially if you are young, as pull-out requires great self-control, experience, and trust. Using caps or condoms is better to prevent pregnancy when you are not sure about your safe days.

4. Symptothermal Method:

This method is a combination of the above mentioned three fertility awareness method (10).

The signs of one FAM will confirm those of the other method. It will be more accurate than the others as you base your predictions on three methods. For instance, tracking your cervical mucus pattern will be helpful when your temperature patterns change due to emotional stress or illness. Moreover, you can identify more safe days to have unprotected sex than by using one method.

You can keep a track of your fertile times by using a fertility pattern chart.

Post-Ovulation Method:

It is another combined method. The days starting from the first day of your period to the fourth day after predicted ovulation are considered to be fertile days. It means you will have very limited safe days, i.e., less than half of a cycle.

The Effectiveness Of Symptothermal Method:

For every 100 couples who rely on this method perfectly for one year, 0.4 (less than one woman) of them gets pregnant.

5. Standard Days Method:

It is like the calendar method which can track your menstrual cycle (11). It is simple but you can use it only if:

  • Your cycles are regular.
  • Your cycle is never longer than 32 days and shorter than 26 days.
  • You do not indulge in unprotected sex from 8th to 19th day in a cycle.

This method uses unique strings of beads, called CycleBeads, which help keep a track of your cycles. You will have 33 colored beads on a string and a movable rubber ring.

  • The first bead is black and has a white arrow
  • The following bead is red
  • The next six beads are brown
  • The following 12 are white
  • The last 13 are brown

Each bead represents a day except the black colored one.

  • On day one, i.e., the first day of the period, put the rubber ring on a red bead.
  • Move the ring from one bead to another every day in the direction of the arrow.
  • Brown beads represent safe days. You can indulge in unprotected intercourse if the ring is on any one of them.
  • White beads represent unsafe days. You should not have unprotected intercourse if the ring is on any of the white ones.
Standard Days Method


The Effectiveness Of Standard Days Method:

For every 100 couples who follow this method perfectly for one year, five women are likely to get pregnant.

The factors that affect the standard day method are:

  • The use of hormonal and emergency contraceptives
  • Intrauterine devices
  • Breastfeeding
  • A recent pregnancy

How Effective Are FAMs In Preventing Pregnancy?

The statistics show that among every 100 couples who use fertility awareness methods for one year, 24 women are likely to get pregnant. The deviations mostly happen if you do not use the methods correctly or consistently. If you practice FAMs appropriately, one to nine women have the probability of getting pregnant.

These methods will work effectively if you:

  • Follow the instructions carefully.
  • Have a single sex partner, who is also are committed to FAMs.
  • Check and chart your fertility signs.
  • Do not mind using pull-out, diaphragm or a cervical cap, spermicide, sponge, latex or female condoms on fertile days.

The fertility awareness based methods can be effective only if your partner cooperates with you. This is the reason why both should know about these methods.

Advantages Of Using FAMs For Avoiding Pregnancy:

  • Inexpensive, convenient and safe to use (as no hormones or devices are used).
  • Develop communication, responsibility, and cooperation among partners.
  • Helpful in establishing an optimum fertility phase to plan a pregnancy.
  • Helps you track and improve premenstrual syndrome (PMS) symptoms.
  • Acceptable for those couples with religious concerns about artificial contraceptive methods.
  • No medications involved.
  • You can get calendars, charts, and thermometers easily.

Disadvantages Of Using FAMs:

  • The failure rate is high as an accurate prediction of fertility is difficult.
  • There will be no protection against sexually transmitted infections.
  • You should keep a close track of your infertile days.
  • Taking any medicine can affect the signs of these methods.
    You should abstain from sex or use a contraceptive for about 10 fertile days in each cycle.

You Cannot Depend On FAMs If:

  • Your periods are irregular.
  • Your partner is not cooperative.
  • You have any STIs or abnormal vaginal discharge.
  • You cannot keep a track of cycles.
  • You are breastfeeding, in teenage or nearing menopause stage as hormonal changes may affect the signs.
  • You had recently taken a contraceptive.

How Can You Have A Safe And Enjoyable Sex?

Now you know about the safe days for having unprotected sex, here are some ways to have safe and enjoyable sex.

1. Get A Test:

You can only be relaxed when you and your partner are infection-free and clean. Schedule regular visits to your doctor to make sure you are not carrying any infections. It is advisable for women to visit a gynecologist once a year for Pap smears and pelvic examinations to check if they carry any viral sexually transmitted diseases.

2. Condoms:

They are better than any other contraceptive method to enjoy safe sex. They prevent unplanned pregnancies and also the risk of STIs. Though they are not 100% safe, they are known to reduce HIV by 85% and genital herpes by 30%. Develop the habit of using them.

3. Lubricants:

Vaginal lubrication will enhance sexual pleasure for you and your partner. You cannot enjoy sex if the vagina is dry as it can lead to irritation, pain, and injury. Oil, water, and silicone-based lubricants are available in the market.

4. Have That Anticipation:

You can try out different ways to build that anticipation in your partner. Buy some interesting stuff or leave a message to him about having a perfect intercourse. It will enhance your moods.

5. Try New Positions and Places:

Do not always use the bed. You can try various locations and positions to have more fun. Having an intercourse while taking a bath would be interesting. Having it in a hidden place in a public spot can be exciting. Do some research on best sex positions and add spice to your experience.

6. Sex Toys:

They can bring pleasure to your sex life. You can get various dildos, vibrators, feathers, massage oils, flavored lubricants and colored condoms to enhance your fun.

7. Sex Play:

Sex play can make your act exciting and adventurous. Playing strip poker or the adult version of truth or dare can make it enjoyable.

Frequently Asked Questions

1. Can I have sex during my period?

Yes, you can have sex on your period unless you are uncomfortable. You may feel inconvenient as it can be messy because of the oozing blood. But for many, libido increases during periods. You might have a chance to contract sexually transmitted diseases, so, use contraception.

2. How many days after period do I ovulate?

Ovulation occurs 14 days after your period, if your cycle is regular. If you have an average 28-day menstrual cycle, you will ovulate around 14th day. If the cycle ranges from 26 to 32 days, you will ovulate anytime between 12th and 19th day.

3. Are there any chances of getting pregnant if I have sex right after my period?

The probability is low. Your chances of getting pregnant increase as you move into your fertility window. Having intercourse without contraception can increase the chances of pregnancy during your fertile period.

4. When can a woman not get pregnant?

There is no particular phase when a woman cannot get pregnant as ovulation and menstrual cycles are unpredictable at times. However, you can use certain fertility awareness based methods to track your safe sex days so as not to conceive.

Hope you have got a clear understanding of the safe period to avoid pregnancy. Do share your experiences in the comments section.

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