About the Pregnancy Due Date Calculator
Find out when your baby is due. Enter the first day of your last menstrual period (and your usual cycle length), or your conception date if you know it, to estimate your due date.
You will also see how far along you are, which trimester you are in and the dates of key milestones. Only about 1 in 25 babies arrives exactly on the due date — most are born within two weeks either side. Results are estimates for general information and are not a substitute for advice from a doctor or other qualified health professional.
How to use the Pregnancy Due Date Calculator
- Choose “Last period” or “Conception date”.
- Enter the date (and your average cycle length if using your last period).
- See your estimated due date, current week and milestone dates.
Frequently asked questions
How is the due date calculated?
Using Naegele’s rule: 280 days (40 weeks) after the first day of your last period, adjusted if your cycle is longer or shorter than 28 days. From a conception date it is 266 days (38 weeks).
Why is pregnancy counted from my last period?
Because the date of ovulation is rarely known exactly, doctors count from the last period. That means you are considered about two weeks pregnant at conception.
Can my due date change?
Yes. An early ultrasound scan often gives a more accurate date, and your midwife or doctor may adjust it.