Due Date Calculator

The Due Date Calculator estimates when your baby is due from the first day of your last menstrual period or from your conception date. Along with the due date, it shows how many weeks and days along you are today, which trimester you are in, and how many days are left — a quick way to picture your pregnancy timeline.

How to use the Due Date Calculator

1. Choose whether to calculate from your last period or your conception date.
2. Enter the date — the first day of your last period, or the date you conceived.
3. If you used your last period, adjust the average cycle length if it isn't 28 days.
4. Read your estimated due date, how far along you are, your trimester, and the days to go.

Frequently asked questions

How is the due date calculated?

It uses Naegele's rule: the due date is 280 days (40 weeks) after the first day of your last period. For cycles longer or shorter than 28 days, the date is shifted by the difference. From a conception date, the due date is 266 days (38 weeks) later.

Why is pregnancy counted from my last period and not conception?

Most people don't know the exact day they conceived, but they usually know when their last period started. So pregnancy weeks are counted from that date, which is about two weeks before ovulation and conception.

How accurate is the due date?

It's an estimate. Only around 4–5% of babies are born on their exact due date, and most arrive within a week or two either side. An early ultrasound can give your care provider a more precise date.

Is this medical advice?

No. The result is for general information only. Your doctor or midwife will confirm your due date and guide your prenatal care.