How the Natural
Cycles° app works

Natural Cycles is an FDA Cleared app that has helped millions of women support their fertility journey. From preventing to planning, following pregnancy, and recovering from birth — the NC° app provides content tailored for you every step of the way.

The app is powered by an algorithm that analyzes hormone-driven changes in your body temperature to let you know when you’re fertile or not.

Natural Cycles is the first and only app of its kind cleared by the FDA as birth control. Many fertility apps are based on a 28-day cycle. This means the fertile window they predict is not personalized to your cycle. So, how can it be true to you? Our algorithm uses your unique temperature and cycle data to significantly reduce the risk of an incorrect fertility status, helping minimize unintended pregnancy and support pregnancy planning with greater precision.

Plus, privacy protection isn’t included with all apps, but it is with your NC° subscription. With NC° Secure, your cycle data is private and secure.

To get started:

1. Sign up for Natural Cycles
   (purchase a subscription and measuring device)
2. Download the app
3. Follow the steps to set up your device
4. Start measuring!

Birth control costs money to make and supply. A subscription to the Natural Cycles app helps make hormone-free birth control more accessible, giving you more choices to find what works for you — all while supporting women’s health research.

Because we charge a subscription, we don’t need to profit from selling users’ data like some “free” apps do. Natural Cycles is committed to data privacy, and as a regulated medical device, we are required to comply with the FDA’s cybersecurity requirements.

We offer two plans: annual or monthly. Click here to find the right subscription option for you.

Yes. The effectiveness of Natural Cycles is supported by clinical evidence, which shows Natural Cycles is 93% effective with typical use. When used as intended, i.e. if you never have unprotected intercourse on Red Days, Natural Cycles is 98% effective. Read more on the science behind our effectiveness.

Forgetting to measure doesn’t impact how effective NC° Birth Control is at preventing pregnancy. However, if the app doesn’t have enough data due to poor sleep or forgetting to measure, you might get more Red Days (when you’ll need to abstain from sex or use protection).

You don’t have to wait for Natural Cycles to learn your cycle before you can start using it because Natural Cycles is effective from the first day of use!

Natural Cycles is committed to protecting your data. We have strong security protocols, including encryption and pseudonymization, to keep your data secure. As a regulated medical device, Natural Cycles is required to comply with the FDA's cybersecurity requirements. And as a Swedish-based company, we are designed to comply with GDPR standards, pledging to safeguard your data no matter where you live. Learn more about how we protect your data here.

Natural Cycles° is a non-hormonal, non-invasive form of birth control. Because it doesn't contain hormones or require any medical procedures, there are no physical side effects associated with using the app itself. Instead, Natural Cycles° works by helping you understand your fertility through temperature tracking and cycle data.

Natural Cycles is just as effective if you have irregular menstrual cycles (i.e. cycles lasting fewer than 21 days or greater than 35 days in length). 

If your cycle is very irregular, Natural Cycles may be less suitable for you, as you may be given more Red Days (these are a safety buffer since ovulation days can change with irregular cycles). 

However, those with irregular cycles often find that Natural Cycles is a useful tool for tracking their irregularities and better understanding their bodies. Find out if Natural Cycles could work for you.

If you're using non-hormonal birth control (like condoms or copper IUD), you can start using Natural Cycles right away. If you're using hormonal birth control, you'll need to stop using it before starting Natural Cycles, as hormones can affect your cycle and temperature. It's also common to experience cycle irregularities after stopping hormonal birth control. Speak to your healthcare professional if you have any concerns. 

Absolutely. Natural Cycles goes beyond birth control. Learning about your cycle also gives you the power of knowing when it’s the best time to conceive. NC° Plan Pregnancy tells you the days when you are most fertile, and it can also let you know when it’s the optimal time to take ovulation or pregnancy tests. Once you log a positive test in the app, you can start using NC° Follow Pregnancy – here, you’ll get regular updates on the progress of your pregnancy.

To use NC° Plan Pregnancy, you need to measure your body temperature, input your temperature and period data, and then the Natural Cycles algorithm will provide your daily fertility status. In NC° Plan Pregnancy, the fertile window is presented in a scale of red colors, where the most fertile day has the darkest shade of red, and the lightest red color indicates that fertility is less likely. Non-fertile days have a light green color. 

Natural Cycles gives you the information you need to time intercourse and maximize your chances of conceiving. Research shows that couples using Natural Cycles get pregnant in 3 cycles on average. 

Your body temperature naturally changes throughout the day in response to factors like physical activity, food, stress, illness, and your environment. To identify the subtle temperature changes associated with ovulation, the NC° Fertility Algorithm needs a more stable measurement.
Overnight temperature data captures your body's resting temperature while you sleep, before daily activities can influence it. This provides a clearer signal for the NC° Fertility Algorithm to analyze, helping it identify ovulation and estimate your fertile window more accurately.
That's why Natural Cycles uses temperature measurements collected overnight or first thing in the morning when your body is at rest — it's the most reliable way to track the temperature patterns that occur throughout your cycle.

No. Unlike calendar-based methods, Natural Cycles doesn't rely solely on cycle dates or assume ovulation happens on the same day every month.
Traditional calendar methods estimate fertility based on previous cycle lengths and fixed assumptions about when ovulation is likely to occur. However, cycle length and ovulation timing can vary from cycle to cycle, making calendar-only predictions less reliable.
The NC° Fertility Algorithm analyzes your temperature data alongside your cycle information to identify ovulation and determine your fertile window. Rather than applying the same formula to everyone, the NC° Fertility Algorithm adapts to your unique cycle patterns and updates its predictions as new data is added.
Research comparing Natural Cycles to calendar-based methods found that the individualized algorithm was better at identifying the fertile window and was less likely to incorrectly classify the most fertile days as non-fertile

Like traditional basal body temperature (BBT) methods, Natural Cycles uses body temperature to help identify ovulation and understand fertility. The difference is that Natural Cycles combines temperature data with cycle information and optional ovulation test results, then uses the NC° Fertility Algorithm to analyze that data and provide a daily fertility status.
Traditional BBT methods typically require taking your temperature with a thermometer every morning and manually interpreting temperature patterns over time. With Natural Cycles, the algorithm does the analysis for you — no manual calculations or charting required.
Natural Cycles can be used with the NC° Band, as well as other compatible wearables, including Oura Ring, Apple Watch, Garmin devices, making it easier to collect temperature data while you sleep (versus manually taking your basal body temperature upon waking up each morning).
Unlike traditional BBT methods that often require a learning or trial period, Natural Cycles is effective from day one when used as directed.