New update in the Natural Cycles app: The Algorithm and the Predictions.

We are very proud to announce the improvements that our team has been focusing on over the past few months. We’re always striving to improve, and make the experience of using Natural Cycles simply  easier and better.  This time the focus has been on the algorithm and the new look of the predictions.

An optimised algorithm

Thanks to all your amazing data, the algorithm has now been updated and optimised to find ovulation with 10% higher precision.  If you are using Natural Cycles to prevent pregnancy this means that you could get more green days. If you are using Natural Cycles to plan a pregnancy, this means your fertile window will be more accurately pinpointed.

Smarter and clearer predictions

The predictions in both daily and the calendar view will have a new look.  (See below.) As you know predictions are only a prognosis for upcoming days, and might change as you add data. Therefore, they will now be visually different from past days and the current day, and will be shown in a grey color with a smaller circle that shows the prediction.

Another thing that will be new is the number of predicted cycles. In the calendar view you will see five predicted cycles, regardless of your cycle regularity. Smart, right?

As you might know, the predictions will get better the more you use Natural Cycles, and the more data it has.  

A smarter view of history

A lot of Cyclers have used Natural Cycles to prevent pregnancy, then switched to plan a pregnancy, or the other way around. Now, you will be able to see this visually in the graph, monthly and history view. This is a great way to track when you’ve switched to which plan.


Hope you’re excited as us about these upcoming changes. Any thoughts or feedback? Please comment below!

Your Natural Cycles Team

The best time to get started is now.

Just before the New Year hits we often make resolutions for the upcoming year. The best time for new beginnings is now, and a small habit can make a big change.

When using Natural Cycles you will not only know your most fertile days, you will also know more about your health, mood and energy levels which will help you plan your new year better and get in touch with your body.

Learn more about few Cyclers and their experiences with Natural Cycles:


Since the envelope with the thermometer and a the nice purple booklet dropped into my mail box, I felt like Natural Cycles has been a safe choice. You have always responded carefully and thoughtfully to all the questions that I had – I’m sure many other women can relate. I like that you continuously send out emails with information concerning so much helpful knowledge about our bodies and measuring temperature. This is something I haven’t experienced before. You really do a great job and I really wish more women find you so they can have my experience.

Emilia, Sweden.








When I found Natural Cycles on Pinterest, I was really happy to have found a method that suited me. I like Natural Cycles because it is natural and it makes me learn a lot about my body.”

Anne-Charlotte France.







I really wanted to get pregnant a long time. My partner and I had tried for almost 1,5 years. Then I got pregnant after 6 months of using NC! What I like the most about it is that the algorithm can calculate everything even though my cycle is irregular. I also really like the personalized messages you get.

Josefina, Sweden.








I started with Natural Cycles because I didn’t know when I had ovulation and since we wanted a second baby, this seemed like the best way to get to know my body. I like NC because it is so precise and helped me find my fertile days each month. For example, I never tested positive for LH tests before since I’ve tested the wrong days.





If you feel inspired to make a New Year’s resolution to get to know your body and cycle, give Natural Cycles a try.

Thank you Cyclers.

Now that 2016 is coming to a close, it’s time to reflect, think back and plan what we want to achieve next year.

It has been a big year for Natural Cycles. We’ve accomplished several milestones and have battled the occasional hurdle along the way. Closing an important investment round allowed us to further expand the team and we’ve published another clinical study on the effectiveness of Natural Cycles. We’re also beyond proud that our CTO and co-founder Elina Berglund was chosen as one of the most influential and impactful individuals in the Nordic technology and startup scene, and Natural Cycles being announced as one of the top 10 apps in the App Store for 2016.

Women’s health is our number one priority and we believe that pushing for progression in this field is extremely important. We’d like to thank every single one of you for being a part of Natural Cycles, by contributing and helping us to become a better company every day.

We’re extremely excited for the upcoming new year and to see what challenges it brings.
Thank you and happy holidays!

How does the Natural Cycles algorithm work?

Behind the Natural Cycles app lies an unique algorithm that calculates your green and red days. This is the brains behind the app that pinpoints and predicts your ovulation, and the days you are fertile. What you might be wondering is how does it know when you are fertile or not?

natural cycles algorithm


The algorithm works by identifying your fertile days. These six days are calculated by taking your ovulation day and the five days before, because of possible sperm survival, into account.

Every woman and every cycle is unique, so the algorithm will have to get to know your cycles before it can tell you when ovulation has occurred. That’s why you might have more ‘red’ fertile days in the app when you get started with Natural Cycles.


Your basal body temperature shifts after ovulation and becomes higher due to release of the hormone progesterone. So the algorithm takes your temperature measurements and optional LH tests into account when calculating and pinpointing your ovulation and most fertile days. The app will let you know what your average temperature values are in luteal vs follicular phase, how your temperature curves look and get an overview of your fertile days. The algorithm will also calculate your predictions for the months ahead, depending on how regular your cycles are.



The longer you use Natural Cycles, the better it gets to know you.  It takes your cycle irregularities into account, the variation of your cycles and ovulation day, temperature fluctuations, length of follicle and luteal phase. On average, it takes up to 3 cycles for the Natural Cycles algorithm to get to know your cycles and gives you more and more green days.

The longer you use Natural Cycles, the better it get’s to know you.  You can see your irregularities in your stats page.  

Want to explore the powerful knowledge that lies behind our algorithm’s calculations? Sign up today and get to know yourself and your body better.


Winter is here: will it affect my basal body temperature?

Generally speaking your body should not be affected, given that you have normal bedding (what you usually use) and room temperatures at home. Your body is great at maintaining a regular temperature and will adjust to the cold weather!


With Natural Cycles it is important to measure your basal body temperature in your mouth and underneath your tongue. By closing your mouth and breathing through your nose you can avoid external factors like room temperature influencing it. This is why measuring your temperature on your skin or in your ear is not accurate enough to use with the app.

We also want to point out that electric blankets and heating pads can have an effect, so keep an eye on your temperature curve when using these. Winter is also the time of year where a lot of us get sick, so if you feel unwell and your temperatures are much higher than usual be sure to disable the measurement until you feel better again.

If you haven’t entered any temperature, you cannot click on inactive.


Read more about measuring the basal body temperature related articles here:

When and how to measure basal body temperature.

Why should I use a basal thermometer?

What if I forget to measure?


Happy Cycling!

Let’s talk about PMS!

When does PMS occur?

About one week before your period begins you may experience some premenstrual symptoms which include both emotional and physical symptoms that can go anywhere from acne and physical pains to feeling very tired.  By knowing when your period is due, you will know approximately when to expect PMS. 

Who suffers from PMS?

Every woman and every menstrual cycle is different and PMS symptoms can vary hugely from one person to the next. A study from the American College of Obstetricians and Gynecologists has shown that around 85% of women suffer under at least one PMS symptom. While some women only experience slight discomfort, others are hugely affected.  We feel you ladies, so we want to discuss PMS and some common symptoms.

What are common PMS symptoms?  

It is said that the changes in hormone levels and chemicals within the brain have an affect on periods. However, specific reasoning is unknown. These are the most common symptoms and what you should look out for:

Emotional Symptoms:

  • Mood swings and irritability or anger
  • Crying spells
  • Appetite changes and food cravings
  • Trouble falling asleep (insomnia)
  • Social withdrawal
  • Poor concentration
  • Tension or anxiety
  • Depressed mood

Physical Symptoms:

  • Joint or muscle pain
  • Headaches
  • Fatigue
  • Weight gain related to fluid retention
  • Abdominal bloating
  • Breast tenderness
  • Acne flare-ups
  • Constipation or diarrhea

How can Natural Cycles help with your PMS?

Because these symptoms can be pretty tough to deal with, Natural Cycles will give you gives you an advanced warning when you may experience PMS symptoms next. As the app gets to know your body you will receive a personal message once it recognizes that your period is due. That way you can always plan ahead and sudden symptoms or the arrival of ‘aunt flow’ or PMS won’t come unexpectedly anymore.


Try out Natural Cycles yourself and always know where you’re at in your cycle. 


The colors in plan a pregnancy mode

Dear Cyclers,

In the new version of the Natural Cycles app the pregnancy mode has a new fresh look. The ‘fertile window’ is presented in red scale where the most fertile day is red, and the least fertile day is pink. Read more about the fertile window and the science behind our menstrual cycle here. The non-fertile days are presented in grey.


“We want the important days to stand out very clear, even if this means that the non-fertile days come across as dull. We do this by using the contrast between a muted gray and a very vibrant red.” Quote from our head of design, Daniel.

If your ovulation has been confirmed in the app, you will also be able to see when you can test for pregnancy the earliest. This function also existed in the old app, but is now even more visually clear. If your period comes, the symbol will disappear. Read more about symbols here.


Do you have any feedback? Comment below, please! 🙂



Meet a Cycler – Pauline


My name is Pauline and I’m studying to become a priest. I’ve used Natural Cycles for almost a year now and both me and my partner feel satisfied beyond all expectations. Through Natural Cycles I’ve learnt so much more about myself and my body, which I find as very valuable knowledge that I wish all women could have access to. For example, I did not know that women are only fertile six days per cycle. Choosing to start with Natural Cycles is one of the best decisions I’ve made in my life, and my advice to you who are considering to start with Natural Cycles is simply that it’s worth it!



Thank you Pauline for sharing your experience with Natural Cycles.
Do you want to be our next Meet a Cycler story? Don’t hesitate to get in touch at





Natural Cycles Graph Update

Dear Cyclers,

You may have encountered difficulties to access your graph in the new app – for example, a ‘blank screen’ appears or the graph does not load properly. This software bug has been fixed several weeks ago, but we are waiting for the new update to be released in the App Store! It will be available soon.

In the meantime, you can still get it to work! What happens is that the graph icon is highly sensitive and if you tap on it for ‘too long’ or click on it multiple times it will ‘break’ (meaning it will not load at all or appear as a white screen.)

What you can do if this happens is the following:

  1. First you need to close the app and re-open it. (Double-click your home-button on iPhone and slide up the NC app)
  2. When you enter the app again, click only very softly/quickly on the graph-icon and wait for it to open. It should work!

If you cannot wait, note that you can always access Natural Cycles through our web-app to get the latest version:

We apologize for the inconvenience and thank you for your patience.

We’re also currently working really hard on creating the best user experience for you and we would love to hear your feedback:




The new graph will have a custom design optimized to be viewed on a phone. It will be displayed in landscape mode on your phone for best overview and we have tried to make it cleaner, with less visual noise.

It will also be supplemented by a history list view. Each day will be listed with icons indicating what happened on that day and what data you added. Does this sound like something useful for you Cyclers? Would you use it?


 Pasted image at 2016_01_04 01_40 PM




















We would love to hear your feedback regarding the new graph design so please comment below with your thoughts!

Have a great day!

The Natural Cycles Team

What’s new about the Natural Cycles app?

Dear Cyclers,

You can now download the new updated version of the Natural Cycles app. We worked really hard to improve it and listened to all of your valuable feedback. We’re super excited and proud of it, and we hope you’ll like it as much as we do!

Along with the major design changes, we have even more news! Natural Cycles is now available on Apple Watch, and the Natural Cycles algorithm has been updated to even more accurately find and narrow down your fertile window.


Track your Fertility mode

Safety is our number one priority and it was therefore important to make sure that the new design reflects what’s most important about Natural Cycles.

  • The focus in the new app is on today’s fertility status – red or green.  Simple!
  • Below your current fertility state, you can see your predictions for the week. Here, it was very important to make clear that predictions may change in the future and should not be taken for granted – just like with the weather.
  • After today’s current view, you can switch to have a monthly overview presented to you as a calendar. Here again, it was very important to separate your past fertility from future predictions.
  • If you want to dig a little deeper into your data, you can have a look at the graph as well as your cycle statistics.


The new design is a result of several thousands of hours listening, analyzing and engaging with your feedback. Thank you!


Below, you will find an explanation of the icons as well as some answers to most common questions.


prevent overview


How to enter data


To enter your daily data, click on the + in the upper right corner. Enter your temperature and if you want to add any additional data, such as ovulation test result or a note, you click on “additional data”.  Click ‘save’ and you’re all set! In this view you can also swipe to the left to go back in time to see your previously entered data. If you have entered any data and then swipe back, your data will be saved automatically!


How to access the graph?

the graph view

You can access your graph under the “today” view by tapping on the graph symbol in the upper right corner – we are currently working on further improving the graph, so stay tuned!



Changes in the algorithm

With significantly more data from all you Cyclers, we were able to optimize our algorithm for the new app such that it will identify and predict ovulation and your fertile window with even greater accuracy. This update in algorithm might lead to small changes in the history of your data, which means that you might see a previously red day change into a green day, and vice versa. This is normal because we run a new, improved algorithm over your entire dataset. You do not need to worry about this – important is to always check today’s fertility status!


Natural Cycles Plan mode


For Natural Cycles Plan users, we focused on clearly highlighting your most fertile days. The most fertile days are indicated in red, while your less fertile days will be shown in different shades of soft pink colors. Your non-fertile days are shown in  a light grey color.
overview plan

We’re excited to hear your feedback,


All the best,
The Natural Cycles Team