Signs your period is coming tomorrow

You can also use this period calculator to find out what is your fertility window – that is, the time when you're most likely to get pregnant.

As sperm can live up to seven days inside your body, you should assume that the fertility window starts seven days before ovulation (see ovulation calculator).

How to calculate period cycle

It ends approximately one day after the ovulation, though, as the egg lives for about 24 hours.

Ovulation is when an egg is released from your ovaries. This is the time when you are most fertile. It usually happens about two weeks before the start of the next period.

If you want to have a more precise estimate, you should monitor your body temperature and the changes in cervical mucus.

You can keep track of your menstrual cycle and ovulation with the use of our basal body temperature calculator ⬅️ Check our tool for more details.

💡 You might also be interested in our pregnancy weight gain calculator.