Pregnancy Due Date Calculator
Find your due date, how many weeks pregnant you are and the key dates ahead, from your last period, conception date or IVF transfer.
How the due date calculator works
Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception, which usually happens about two weeks later. A typical pregnancy lasts 40 weeks, or 280 days, from your LMP. That is why you are already "4 weeks pregnant" when your period is late.
If your cycles are longer than 28 days, you probably ovulated later, so the calculator moves your due date later by the same number of days. Shorter cycles move it earlier.
Due date calculator FAQ
How is a due date calculated?
Most providers use Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle is longer or shorter than 28 days, the date moves by the same number of days. From a known conception date, add 266 days (38 weeks).
How accurate is my due date?
A due date is an estimate. Only about 4% of babies are born on their exact due date, and most arrive within two weeks either side. An early ultrasound, ideally in the first trimester, is the most accurate way to date a pregnancy.
What if I had IVF?
For IVF, the due date is calculated from the embryo transfer date: add 261 days for a day-5 (blastocyst) transfer or 263 days for a day-3 transfer. Choose the IVF option above.
When is the first trimester over?
The first trimester ends at the end of week 13. The second trimester runs from week 14 to week 27, and the third trimester from week 28 until birth.
What does full term mean?
Babies born from 37 weeks are early term, 39 weeks 0 days to 40 weeks 6 days is full term, 41 weeks is late term and 42 weeks or later is post term.
This calculator gives an estimate only. Your provider may adjust your due date after an ultrasound.