Pregnancy Due Date Calculator
Estimate your due date, current gestational age and trimester from the first day of your last period, your conception date, or an IVF embryo transfer date.
Not medical advice. This calculator gives an estimate only and is not medical advice. Roughly 4% of babies are born on their exact due date. Always confirm your dates with your midwife or GP, ideally using an ultrasound dating scan, and speak to a healthcare professional about your pregnancy.
Enter your dates
Your estimated due date, gestational age and trimester appear here once you enter a date.
How your due date is calculated
Most due dates are worked out using Naegele's rule: the first day of your last menstrual period (LMP) plus 280 days (40 weeks), adjusted if your average cycle is longer or shorter than 28 days. If you know your exact conception date, your due date is 266 days after that. For IVF pregnancies, the due date is dated from the embryo transfer instead, 261 days after a day-5 (blastocyst) transfer, or 263 days after a day-3 transfer. Gestational age (how many weeks pregnant you are) is always counted from the LMP or its equivalent, which is why it can differ slightly from your actual conception date. A pregnancy is considered full-term between 37 and 42 weeks.
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