Period calculator: Predict your next period & ovulation

How do period calculators work?

Our period predictor is here to help you estimate when your next menstrual cycle will start. Based on your cycle and period length this tool calculates your predicted period start date and can also give an estimate of when ovulation might happen. 

This period calculator uses date calculations only, and does not work in the same way as the NC° algorithm that is part of the Natural Cycles app, a registered medical device. Period calculators should never be used as birth control as they are not medical devices, and menstrual cycles can vary in length and regularity.

If you want to understand a more accurate picture of your cycle, download the Natural Cycles app. As a temperature-based certified birth control method, it provides a more in-depth picture of cycle predictions and can even confirm your ovulation day [1].

What is the menstrual cycle?

The menstrual cycle is the name for the process your body goes through as it prepares for a potential pregnancy. Menstrual cycles start when we get our first period at puberty and can continue until we reach menopause. Our cycles are regulated by a number of sex hormones, such as estrogen and progesterone. The most well-known part of the cycle is probably menstruation. However, there is more to the cycle than your period. Read on to learn more about ovulation and the different cycle phases.

How long is my cycle?

How long your menstrual cycle lasts is very individual. Some people have regular 28-day cycles, while others have longer or shorter cycles. Some people have cycles that vary in length from one month to the next. Recording your cycle length is a great way to learn what’s normal for you, help you spot patterns, and get to know your cycle better.

A textbook cycle is considered to be 28 days long. However, published research from Natural Cycles found that the average cycle length was actually 29 days [2]. Conditions like PCOS (polycystic ovary syndrome) can also cause cycle irregularities [3].

Did you know cycle length typically gets shorter as we get older? It’s also common to experience more irregularities in our cycles as we approach menopause [4].

What is ovulation?

Ovulation is the release of the female egg cell from the ovaries. This usually happens towards the middle of the cycle.The egg cell travels down the fallopian tubes. If it meets a sperm cell and is fertilized, this can lead to pregnancy. An egg cell can survive for between 12-14 hours. If it’s not fertilized, it will disintegrate.

What is the fertility window?

The fertile or fertility window is the time in your cycle when you can conceive. It lasts six days, including the day of ovulation and the five days leading up to it as sperm can survive in the female reproductive system for up to five days.

What are the different cycle phases?

Your cycle is split into two key phases: the follicular phase and the luteal phase. The follicular phase is the first stage of the cycle and starts on the first day of your period. This cycle phase ends with ovulation (the release of the egg cell).

The second half of the cycle is known as the luteal phase. During this phase, your body is preparing for a potential pregnancy. If pregnancy doesn’t occur, then your body prepares to shed the lining of the uterus. And a new cycle begins with your period.

Signs your period is coming

Natural Cycles uses temperature changes to predict and confirm your ovulation and period. As well as temperature changes, there are a number of other signs that can indicate your period is on its way. Here are a few to look out for:

• Tender or sore breasts
• Cervical mucus dries up
• Mood changes
• Headaches
• Cramps
• Food cravings
• Feeling bloated
• Breakouts or pimples
• Lower sex drive

Prevent pregnancy hormone-free

With the Natural Cycles app, you can track all of the above changes and use this info to spot patterns in your cycles. Don’t make menstruation a guessing game. Get more accurate predictions and find out when your period is due based on the science of basal body temperature.

FDA Cleared for use as birth control, Natural Cycles is powered by an algorithm that learns the pattern of your cycle so you can take control of your fertility. Whether you want to plan or prevent pregnancy, take our quiz and find out how Natural Cycles can support your journey.