Pregnancy Due Date Calculator

Find your estimated due date (EDD), how many weeks and days pregnant you are, and which trimester you are in.

Key dates

An estimate only. Book antenatal care early; your clinic will confirm the date, often with a scan.

How to calculate your due date

The usual method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). It assumes a 28-day cycle with ovulation on about day 14. If your cycle is longer, ovulation and the due date come later by the same number of days; if it is shorter, they come earlier.

• Due date = first day of last period + 280 days (28-day cycle)
• Due date = conception date + 266 days
• Quick method: add 7 days to the first day of your last period, then count back 3 months and add a year

Worked example

Your last period started on 10 January and your cycle is 28 days. Adding 7 days gives 17 January; counting back 3 months gives 17 October. Your estimated due date is 17 October of the same year. With a 31-day cycle, it would be 3 days later, on 20 October.

How pregnancy weeks are counted

Pregnancy weeks are counted from the first day of your last period, about two weeks before conception. So at the moment of conception you are already counted as two weeks pregnant. A full-term pregnancy is 37 to 42 weeks, with 40 weeks as the due date.

The trimesters

• First trimester: weeks 1 to 13. The baby's organs begin to form; tiredness and nausea are common.
• Second trimester: weeks 14 to 27. Many women feel the baby move for the first time.
• Third trimester: week 28 until birth. The baby grows quickly and gets ready for delivery.

Antenatal care

Start antenatal care as early as you can, ideally in the first 12 weeks. Your clinic will confirm your dates, check your blood pressure and blood levels, and advise on supplements such as folic acid and iron. Go to a health facility straight away if you have heavy bleeding, severe headache, blurred vision, a high fever or if the baby stops moving as usual.

Frequently Asked Questions

Planning a pregnancy? Use the Ovulation Calculator to find your fertile days.