How to calculate your ovulation day

Posted on June 27th, 2013

Tracking your ovulation can help give you a good idea of when you can or can’t fall pregnant during your monthly cycle. Here’s what you need to know.

Gynaecologist and obstetrician, Dr Paul Blaauwhof from the Netcare Rosebank Hospital in Johannesburg, explains exactly what ovulation is and how it works.

What is ovulation?
Ovulation is a part of a woman’s reproductive cycle in which an egg is released by a mature ovarian follicle in order to travel down the fallopian tubes towards the uterus, so it can be fertilised.
Once the egg is released, it only lives for 12 to 24 hours in which it has to be fertilised before it disintegrates. If the egg is fertilised in that time and successfully implants, you fall pregnant. If the egg is not fertilised and no conception occurs, the uterine lining and blood will be shed, which is when you menstruate.

When does ovulation occur?
Ovulation usually occurs halfway between each menstrual period. You’ll ovulate approximately 14 days before the onset of your next menstrual cycle.

The ovulation process explained

  • The first part of the menstrual cycle is called the follicular phase. The first phase starts on the first day of your last menstrual period (LMP) and continues until ovulation. A normal menstrual cycle can last anywhere from 21 days until 49 days.
  • The second half of the menstrual cycle is called the luteal phase. This phase starts from the day of ovulation until your next period begins. This phase is more constant and is usually only 14 days from the day you will start to ovulate until the first day of your next period. You can start to ovulate from as early as day seven and as late as day 35. Sexual intercourse during this period of time can increase your chance of becoming pregnant.

Key facts about ovulation

  • Anything that influences the brain can influence the hormones involved in ovulation. This is why ovulation can be affected if you are stressed or ill.
  • When an egg is in the fallopian tube, it takes three days for it to get to the uterus, which means it takes five to seven days for an egg to get implanted from the date of fertilisation.
  • You can still menstruate even if you haven’t yet ovulated.
  • Some women may experience a slight degree of pain or aching near their ovaries during ovulation. There’s also increased vaginal discharge when you ovulate and your basal body temperature (the lowest temperature attained by the body during rest) in the morning will rise after ovulation.
  • Normally only one egg is released every time you ovulate.

Calculating your menstrual cycle

  • It’s quite difficult to calculate exactly when you are going to ovulate, which is why women sometimes have difficulty conceiving.
  • Measure your menstrual cycle and take your temperature if you want to find out if you are ovulating or when you are going to ovulate. A woman usually ovulates on day 14, but it varies. You can also start to ovulate on day seven if you have a short menstrual cycle or on day 24 if you have a 38-day cycle.
  • Keep a calendar of your menstrual cycle. This will help you predict the date of your ovulation over the course of the months. The longer you keep track of your menstrual calendar, the more accurate your ovulation date will become.
  • Ovulation tests can be bought at the pharmacy. These tests can help you to fine-tune your time of ovulation.

Click here for our ovulation calculator.