Gynaecology Centres Australia - Pregnancy Calculator

How Our Pregnancy Calculator Works

Our pregnancy calculator is a convenient tool to help you estimate the stage of the pregnancy (in weeks). This is calculated based on the date of the first day of your last menstrual period (LMP).

It’s very important to understand that any pregnancy calculator can only provide an estimate of how many weeks a pregnancy is. There are numerous factors that may affect its accuracy.

Why Knowing Your Pregnancy Stage is Important

Understanding the timing of gestation and calculating a pregnancy in weeks is crucial, as it can inform your next steps and enable you to take control of your body and your health. These include receiving timely medical care and advice and exploring your options to make an informed health decision that’s right for you, whichever path forward you choose.

Using Our Calculator Step-by-Step

Using our Pregnancy Week Calculator is easy.

Enter the date of the first day of your last menstrual period (LMP).
Click “Calculate”

You will receive a general estimate of how many weeks the pregnancy is.

Pregnancy Calculator

Understand that pregnancy calculators work on the assumption of a regular 28-day menstrual cycle. Its accuracy can be compromised by factors including irregular or longer/shorter menstrual cycles, estimating an inaccurate LMP date, ovulation occurring sooner or later than expected, and more.

If you can’t remember the date of your last period, use a calendar or diary and try to remember what was happening when you last had your period. Doing this may help you figure out the date it started.

If your cycle is irregular or you don’t know your dates, but you are certain of a specific, known conception timeframe (to within a day or two), you may use a calendar to count back 14 days from when you are sure you conceived and use this date for the pregnancy date calculator. Conception usually occurs 14 days before the next period is due (in a 28 day cycle) or 14 days after the first day of the last period. For example, if you think you conceived 6 weeks ago, then the estimation of the pregnancy stage is 8 weeks. That is how pregnancy is measured. It is always measured from the first day on the last menstrual period, even though conception usually occurs 2 weeks later.

Understanding Your Results and Next Steps

Once you have estimated how many weeks the pregnancy is, consider scheduling an appointment with your GP, gynaecologist, or Gynaecology Centres Australia to confirm your pregnancy status. An appointment with your GP will also enable you to discuss your options and access the medical care you require, as well as support you. If you choose not to continue with the pregnancy and feel you don’t need to speak with anyone about your options, you may contact Gynaecology Centres Australia directly to organise a pregnancy termination procedure. An ultrasound is always done at our centres at GCA, to confirm the pregnancy and assess the gestational stage, before any procedure takes place.

Even if you are unsure about your next steps, seeking timely professional medical advice is critical for your health and well-being.

Dealing with Uncertainty or Irregular Cycles

While a pregnancy date calculator is very helpful for many women and mostly accurate, it may be less accurate when the menstrual cycle dates are unknown, or cycles are irregular or protracted (e.g. a woman may have a regular cycle of anything between 21 and 35 days or longer).

If you believe (or know) you are pregnant, make an appointment to see your professional healthcare provider promptly. They will more accurately assess your dates and refer you for an ultrasound scan to better determine your gestational dates. They can also provide you with access to additional resources and any support you need. Ultrasound is the most accurate tool to assess the site and stage of pregnancy and is always done at Gynaecology Centres Australia.