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Calculator for estimating ovulation, fertility, and due date

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If you're planning to conceive, wondering "when am I most fertile?" is highly relevant. Our ovulation calculator provides a scientific estimate for the ovulation period within the menstrual cycle, the dates when you are most likely fertile, and the estimated due date.

The ovulation calculator is designed not only to estimate the likelihood of your most fertile period but also to calculate a preliminary due date. By using this calculation, you get an estimate of your fertile period, which is essential for planning pregnancy and monitoring your reproductive health.

What is ovulation and when does it occur?

Ovulation is defined as the process where immature egg cells are released. This process occurs around fourteen days (14) before the start of menstruation and marks the most fertile period in the cycle.

The fertile period, also called the "fertile window", begins seven days (7) before ovulation. This timeframe is based on the sperm's ability to survive in the woman's reproductive system. Since an oocyte (egg cell) is only viable for about 24 hours, the fertile window is defined up until the end of the luteal phase. To accurately determine this phase, specific medical formulas can be used, such as the formula the ovulation calculator is based on.

Calculating your ovulation

To use the ovulation calculator, you only need to fill in two things about your menstruation:

  • Your cycle length - A typical menstrual cycle is about 28 days, but it's common for the length to vary by a day or two. If you're unsure exactly how long your cycle is or if you menstruate irregularly, we recommend using 28 days as a starting point.
  • When your last period started - For the calculator to work, you also need to provide the start date of your last period.

When am I most fertile?

The ovulation calculator shows your fertile window for the next three cycles. It means that if you don't succeed in becoming pregnant in June, you have new chances between the 4th and 12th of July or between the 3rd and 11th of August.

Estimated Due Date

An additional benefit is that the calculator also gives you an estimate of your estimated due date if you conceive. The pregnancy is assumed to be 280 days (or 40 weeks) long, but remember that it's quite rare to give birth exactly on the estimated due date. Your baby might arrive a little earlier or a bit later than expected.