Pregnancy Due Date Calculator
How to Use the Due Date Calculator
- Choose how you want to calculate: last menstrual period, conception date or ultrasound.
- Enter the date. For LMP, you can also enter your usual cycle length.
- For ultrasound, enter how far along the scan said you were on the day of the scan.
- Click Calculate Due Date.
How the Due Date Is Calculated
Want the full explanation? Read How Pregnancy Due Dates Are Calculated and What They Really Mean.
- Last period (Naegele’s rule): due date is 280 days (40 weeks) after the first day of your last period, adjusted if your cycle is longer or shorter than 28 days.
- Conception date: due date is 266 days (38 weeks) after conception.
- Ultrasound: the calculator works back from the gestational age reported on your scan and counts forward to 40 weeks.
The Three Trimesters
- First trimester: weeks 1 to 12
- Second trimester: weeks 13 to 26
- Third trimester: week 27 until birth
Important Notice
This tool gives an estimate for general information only. Your doctor or midwife will confirm your due date, usually with an early ultrasound, and will advise you on prenatal care. Please contact a healthcare professional if you have any concerns about your pregnancy.
Privacy
The dates you enter stay in your browser and are never sent to our servers.
Frequently Asked Questions
How accurate is a due date?
It is a good estimate, not a prediction. Babies born between 37 and 42 weeks are considered full term.
What if my cycle is irregular?
An early ultrasound is usually more reliable than a calculation from your last period. Please ask your doctor.
Why is pregnancy counted from the last period?
Conception usually happens about two weeks after the period starts, but the exact date is hard to know, so doctors count from the first day of the last period.