Pregnancy Due Date Calculator
Estimate your due date from your last period, conception date or a known due date — with current gestational age and trimester.
Enter a date to estimate your due date.
When is my baby due?
A full-term pregnancy lasts about 40 weeks, counted from the first day of your last menstrual period. This calculator applies Naegele's rule — the standard method used by clinicians — and lets you start from whichever date you know best: your last period, the date of conception, or a due date a scan has already given you.
Gestational age and trimesters
Gestational age is how far along you are right now, shown in completed weeks and days. It also tells you your current trimester, each of which brings different milestones in your baby's development and your own body's changes.
A note on accuracy
Due dates are estimates. Cycle length, ovulation timing and other factors all play a part, so very few babies arrive exactly on the predicted day — most appear within two weeks on either side. Use this as a helpful guide, and rely on your doctor or midwife and a dating ultrasound for medical confirmation. This tool does not provide medical advice.
Frequently asked questions
How is my due date calculated?
The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. This tool also adjusts for cycle length and can work backwards from a conception date or a due date you already know.
What if my cycle isn't 28 days?
Enter your average cycle length and the calculator shifts the estimate accordingly. Longer cycles usually mean later ovulation, so the due date moves a little later; shorter cycles move it earlier.
How accurate is a due date estimate?
It's an estimate, not a guarantee. Only about 1 in 20 babies arrives exactly on the due date — most are born within two weeks either side. An early ultrasound dating scan is the most accurate way to confirm.
What are the trimesters?
Pregnancy is divided into three trimesters: the first runs through week 12, the second from weeks 13 to 26, and the third from week 27 until birth. The calculator shows which one you're currently in.
Is my information private?
Yes. All calculations happen in your browser. No dates or personal details are uploaded or stored.