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Pregnancy Due Date Calculator

Work out your estimated due date, how many weeks you are, and the dates of the usual scans and check-ups. Choose how you want to date the pregnancy. Everything is calculated in your browser and nothing is uploaded.

28 is the standard. If your cycles are longer or shorter, the due date is adjusted.
Your due date is an estimate. Only about 4 in 100 babies arrive on the exact due date, and most arrive within two weeks either side of it. The calculation uses standard methods (Naegele's rule for a last period, 266 days from conception, and the embryo's age for IVF), and a scan done in early pregnancy is usually the most accurate way to date it. This tool does not confirm or diagnose a pregnancy. Please see a healthcare provider for antenatal care. If you have heavy bleeding, severe pain, or any worry about your health or your baby, contact a clinician or emergency service straight away.

About this tool

Pregnancy Calculator estimates your due date, how many weeks pregnant you are, and which trimester you are in, from the first day of your last period or another starting date. It gives you a quick picture so you know roughly where you are and what to expect next.

Only a small number of babies arrive on the estimated due date. Treat the result as a guide, and rely on your doctor or midwife and any scans for the dates that matter for your care.

How to use it

  1. Enter the first day of your last period, or choose the other starting option if the tool offers one.
  2. Check the cycle length if it is asked for. The common default is 28 days.
  3. Press calculate.
  4. Read your estimated due date, the number of weeks and days, and your trimester.

Example

If the first day of your last period was 12 weeks ago, the tool shows that you are about 12 weeks pregnant, near the end of the first trimester, and gives an estimated due date about 28 weeks ahead.

Tips

  • Book your antenatal care early and keep your appointments.
  • If a scan gives a different date from this calculator, your health professional will usually use the scan date.

Questions people ask

How is the due date worked out?

A common method is to count 40 weeks from the first day of the last period. The tool follows this approach.

Will my baby be born on the due date?

Most babies are born some days before or after it.

What are the trimesters?

Pregnancy is split into three stages: the first trimester runs to about 13 weeks, the second to about 27 weeks, and the third to the end.

Should I rely on it for medical decisions?

No. It is for general information. Your own health care team will confirm your dates.

For general information only. This tool does not give medical advice. Confirm your dates and care with a doctor or midwife.