How To Calculate Days Past Ovulation (DPO)

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Caclulate (DPO) Days Past Ovulation. Marked Calendar.
How To Calculate Days Past Ovulation (DPO)

What Does Days Past Ovulation Mean?

Whether you are trying to conceive or just trying to understand your menstrual cycle and fertility, you have probably come across the term “Days Past Ovulation” or “DPO.”  

Days past ovulation is simply the number of days that have gone by since the day of ovulation. 

Knowing days past ovulation can be helpful for tracking your fertile window (the days you are most likely to get pregnant) or knowing when you can start taking a home pregnancy test. 

To calculate days past ovulation you need to know your ovulation date.  

In this article, I will help you figure out your ovulation date and understand the fertile days of your cycle. 

How To Calculate Days Past Ovulation

How To Calculate DPO (Days Past Ovulation)

Calculating days past ovulation is easy!  

The day you ovulate is considered “Day 0” and each day after that is considered “Day 1,” Day 2,” “Day 3,” etc. 

The hardest part about calculating days past ovulation is figuring out when you actually ovulated! 

There are several ways we can determine when you ovulated, and I will go into more detail on each of these ways below.  

What Happens During Ovulation

Here’s just a glimpse into what happens during ovulation.  

Truth time: When I was trying to get pregnant with my son, I started reading about fertility and my menstrual cycle, and I was SHOCKED by how little I actually knew about my period and ovulating 😆

I decided that I needed more information on how to get pregnant so I bought the book “What To Expect Before You’re Expecting,” from the best-selling author Heidi Murkoff of “What To Expect When You’re Expecting.” This book taught me everything I know about my cycle, including ovulation! 

Whether you’re trying to conceive, or just trying to learn more about a woman’s body (#womenareamazing), I would encourage you to buy your own copy of this quick read. 

In a nutshell… 

Or maybe I should say eggshell… 

Each month you go through the follicular phase.  This is when your ovaries prepare one egg to be released and fertilized (the start of pregnancy) or not (the start of your period). 

Ovulation is when a mature egg is released from an ovary and travels down the fallopian tube.

Your ovaries are full of eggs.  In fact, you are born with all of the eggs that you will ever have! 

Except in rare cases, women have two ovaries (a right and a left ovary) and two fallopian tubes–one fallopian tube on either side connecting the ovaries to the uterus.  

Typically your ovaries take turns releasing the egg, but it doesn’t always happen that way… Nor does it matter!

Ovulation is usually painless and there aren’t obvious signs (like a period) to tell you when you ovulated.  

This makes it really tricky to find the exact day of ovulation.  

Luckily, there are lots of different ways to figure out when your time of ovulation is. 

Using Your Cycle To Find Out When You Ovulate

How long is your cycle? Marked calendar. First day of your period. This cycle is 30 days long.
How Long Is Your Menstrual Cycle?

Normal Cycle

The average cycle length is 28 days.  

Your cycle is calculated by counting the days between the first day of your period to the first day of your next period. 

Ovulation typically happens 14 days before your period.  

So, for an average menstrual cycle, this means you will likely ovulate on the 14th day of your cycle.

How Do You Know If You Have A Regular Cycle?

If you consistently get your period the exact same time each month, you likely have a regular cycle.

If you are tracking your cycle for the first time, you might not know exactly how long your cycle is.  

To calculate the length of your menstrual cycle, find a calendar and mark the first day of your last menstrual period.  

This is Day 1 of your menstrual cycle. 

Then wait for the first day of your next period.  The day right before your next period is the last day of your menstrual cycle.  

You might have to track a few cycles to know if your period is regular (the same length each month) or irregular (different lengths each month). 

Irregular Cycles

An irregular cycle is a menstrual cycle that is different lengths. 

It is totally normal for your periods themselves to be longer some months and shorter others.  

It is also completely normal to have heavier bleeding some months than others. 

Just because your period is different lengths or your flow changes, doesn’t mean you have irregular cycles.  

Your cycle length is calculated by the days between the first day of one period to the first day of the next.  The actual time that you are bleeding doesn’t matter.  

If, after tracking your cycles for a few months you realize your cycle length is off by a few days or more, you have irregular cycles. 

You might have irregular cycles from medical conditions, medicines, or breastfeeding (just to name a few).  Sometimes irregular cycles will become regular again at some point, and some women have chronic irregular cycles. 

It will be more difficult to know when you ovulated if you have an irregular cycle, but not impossible! Read on. 

Using Ovulation Calculators And Apps

Ovulation Calculator

There are many websites that will tell you when you likely ovulated.  

Web MD has an Ovulation Calculator and Calendar.  You can use this as a Days Past Ovulation (DOP) Calculator. 

This method will require you to know information like when your last period was, and how long your cycles are.  These websites can be pretty accurate for people with regular cycles, but will not be accurate for those with irregular cycles. 

Ovulation, Period, and Fertility Apps

Whether you are just tracking your cycle or are trying to conceive, there are several apps on the market that I have personally used that I would recommend.  

The first is Fertility Friend.  This app isn’t the prettiest and has A LOT of features (so it can be overwhelming).  

I really liked the app because there is a free course that you can take within the app that explains your cycle in a lot of detail.  

I also love that you can export pictures of your fertility graphs to show your doctor or fertility specialist.  

The second app that I love is called Premom.  

This app has a very user-friendly interface.  It is clean and simple to use.  

What sets Premom apart from all of the other apps is its ability to read your pregnancy tests and ovulation prediction strips. 

I really like that you can take pictures of your ovulation strips or pregnancy tests and the app will tell you if they are positive! 

Premom sells its own ovulation strips and pregnancy tests specifically designed for the app.  You can find Premom ovulation strips here.

But you can use ANY kind of ovulation strip or pregnancy test (except for digital ones).  

Personally, I used these Pregmate ovulation strips from Amazon (bonus: you get 20 pregnancy tests too) and First Response pregnancy tests for both of my babies. 

With both apps, the more information that you log each day, the more accurate their ovulation predictor will be.  

Signs That You Are About To Ovulate

Aside from apps and websites, your body is going to be the most reliable to tell you when you are ovulating. 

These are the most accurate of the different methods to find out when you ovulated. 

Pro Tip: To have the best picture of your full menstrual cycle, I would suggest using these physical signs WITH one of the apps listed above to get the most accurate picture of your cycle. 

Cervical Mucus

Cervical mucus is secreted from the vagina throughout your cycle.  It can be watery, sticky, creamy, or have the consistency of egg whites.  

Checking your cervical mucus does not have to be an invasive process.  

When you wipe in the bathroom, take note of what type of cervical mucus (if any) is on the toilet paper.  

Egg white cervical mucus (also called EWCM) will happen right before you ovulate.  

If you notice that your cervical mucus looks like egg white, you are likely going to ovulate in the next 24-48 hours. 

Basal Body Temperature

Your basal body temperature (BBT) is your body’s temperature at rest. This is different from a normal temperature because it must be taken first thing in the morning before you even move. If you want to know more, here is an in-depth article on basal body temperature and ovulation.

You need a special thermometer to take your basal body temperature.  

During a woman’s menstrual cycle, the basal body temperature will rise in the 24 hours AFTER you ovulate.  

If you are charting your cycle using one of the apps, you will be able to tell exactly when you ovulated. 

The downside to this method is that by the time you see the spike in temperature, you will be past your fertile peak.  

For this reason, charting your cycle for a few months usually reveals a pattern where women can accurately predict when they will ovulate based on previous months.  

Other Physical Signs of Ovulation

Many women feel physical signs of ovulation the day before or after they ovulate.  

These symptoms are similar to what you experience before or during your period.  

This is not a complete list, but here are some signs of ovulation: 

  • Sore breasts or tender breasts
  • Menstrual cramps
  • A twinge or pain on either side of the ovaries (usually right when the egg is released) 

Pain during ovulation is very common.  It is sometimes called Middleshmirtz.  If you want to know more about pain during ovulation, I have a whole article here

Ovulation Predictor Kits

Besides calendars, charts, apps, and physical symptoms (like cervical mucus, basal body temperature, etc.) the best way to know exactly when you are ovulating is to use an ovulation predictor kit.  I wrote a whole article on ovulation tests, how to use them, when to use them, and how to read the results here.

Ovulation predictor kits have the most accurate results because they measure the LH (luteinizing hormone) in your urine.  

These kits will give you definite positive results or negative results.  

There are many ovulation test kits out there… Usually called OPKs. 

I personally found success with these Pregmate strips.  

The directions were clear and I always got a positive result before ovulation.  

Plus, when used as directed, you could be using 2-3 strips a day as you get closer to your ovulation date, so they are very easy on the wallet compared to other tests.  

One of the drawbacks to testing kits like mine (strips with a control and test line) is that they can be hard to read.  

It might be difficult to tell if something is positive, negative, or somewhere in between.  

If you want to take the guesswork out completely you can buy a digital ovulation predictor kit (OPK).  These kits will tell you when you are about to ovulate.  

For all OPK tests, ovulation will happen within 36 hours of receiving a positive test.  

To Sum It All Up

To calculate DPO you need to know the day that you ovulated.

The best way to know EXACTLY when you ovulated is using your basal body temperature (BBT).  

The spike will occur 24 hours after you ovulate.  Once you get a spike in temperature (that lasts 3 days or longer), you will know that you ovulated the day before the increase. 

Unfortunately, by tracking ovulation this way, you will miss your fertile window.  

To know when you are going to ovulate BEFORE it happens (during your fertile window) you should: 

  1. Chart your cycle using a calendar, website, or app.  
  2. You should also monitor yourself for physical signs of ovulation–ESPECIALLY CERVICAL MUCUS. 
  3. And, you should use an OPK to give you a specific 36 hour window of when you will ovulate.  

Ovulation And Trying To Conceive

If you are trying to conceive, you should chart your cycle and give it 6 months to a year of actively trying to get pregnant before you sound the alarm bells.  

As someone who wanted to get pregnant RIGHT AWAY, I know that is easier said than done.  

While I can’t say that any of these methods will get you pregnant faster, I can tell you that having sex during your fertile window is the key to getting pregnant.  

If you don’t know when your fertile window is, you will be leaving it all up to chance.  

Using an ovulation calendar, tracking physical symptoms, using a fertility monitor (like this cool Ava Fertility Bracelet), and/or OPKs will give you the best idea of when the 6 most fertile days for you are. 

Ovulation And Pregnancy

After the luteal phase, a fertilized egg implants itself in the uterine wall for the pregnancy to continue.  

This time is known as implantation.  

You can use an online implantation calculator like this one to figure out exactly when this happens. 

You might even experience implantation bleeding which is different from your period (very light normally spotting) but is completely normal. 

I have a full article on how soon can you test after implantation here if you want to learn more about implantation. 

If you know your ovulation date and become pregnant, you can use that information to find out how far along you are, and when your due date is.

Days Past Ovulation Frequently Asked Questions (FAQ’s)

How To Calculate DPO?

Now that you know when you ovulated, mark that date on the calendar.  This is Day 0.  

The next day is Day 1, then Day 2, Day 3, etc. 

The Premom app takes all of the guesswork out and marks your DPO on the calendar for you!! 

How To Calculate Your Fertile Window?

When is your fertile window? Marked calendar. Ovulation. Most fertile days.
When Is Your Fertile Window?

If you are using an ovulation calendar or any of the other methods that I have talked about to find your ovulation day, chances are you are either trying to find your fertile window or trying to figure out when you can take a pregnancy test.  

If either of these is you… Read on! 

Fertility charting will give you the best chance of catching your fertile window.  

I love Fertility Friend and Premom for charting. 

Your fertile time is the day you ovulate and the 5 days before it (6 days total).  

The day you ovulate, the egg is released and is only viable for 24 hours max

However, sperm can live inside a woman for up to 5 days.  

So, if you have unprotected sex during your fertile window (on any of the 5 days leading up to ovulation or the day of ovulation), there is a good chance there will be sperm waiting in the fallopian tubes to fertilize your egg when it is released during ovulation.  

Can You Get Pregnant When You’re Not Ovulating?

Yes.  When you have sex the sperm travel to the fallopian tubes. 

The BIG CATCH is that sperm can live for up to 5 days inside the fallopian tubes.  Because of this, you can get pregnant for 5 days leading up to ovulation and the day of ovulation itself. 

What Happens After Ovulation?

After ovulation one of two things happens: 

1. You get your period

2. You are pregnant 

You won’t know either right away.  

Immediately after ovulation, your body goes into the luteal phase.  Think of this as your body’s natural “waiting period.” 

The luteal phase is usually around 14 days long but can be longer or shorter for different women

If the egg was fertilized, it will start producing progesterone which tells your body not to shed the uterine lining. Congrats! You are pregnant! 

If at the end of your cycle the egg was not fertilized and no progesterone is detected, your body will automatically shed the uterine wall… Which is your period!  

Women’s bodies are amazing 😊! 

When Should You Take A Pregnancy Test?

Most pregnancy tests are not going to be accurate until the day of your missed period.  

Home pregnancy tests measure the human chorionic gonadotropin (HCG) in your urine.  

HCG increases as your baby grows, but typically cannot be detected in over-the-counter tests until 14 days after ovulation.  

There are more sensitive tests on the market now like the Family First 6 Days Sooner tests that will detect HCG around 8 DPO.  I got both of my positive pregnancy tests at 8 DPO with these tests.  

If you need to determine pregnancy before 8 DPO you should talk to your healthcare provider.  They may be able to do a urine test that is more sensitive or do a blood test to detect pregnancy.