Health & Fitness
Pregnancy Due Date Calculator
Estimate your due date, see how many weeks pregnant you are, and find your trimester dates — all calculated privately in your browser.
Pregnancy due date
Enter a date above to estimate your due date.
How the due date is worked out
Pregnancy is counted from the first day of your last menstrual period, not from conception, because that date is easier to pinpoint. A typical pregnancy lasts about 40 weeks (280 days) from that day. Because ovulation timing depends on your cycle length, we adjust the estimate when your cycle is longer or shorter than the usual 28 days. The result is the same approach your doctor uses before confirming with a scan.
Frequently asked questions
- How is my due date calculated?
- The most common method (Naegele's rule) adds 280 days — 40 weeks — to the first day of your last menstrual period (LMP). We also adjust for your cycle length, since a longer or shorter cycle shifts the likely ovulation and conception date. If you know your conception date, we add 266 days instead.
- How accurate is a due date calculator?
- A due date is an estimate, not a fixed date. Only about 1 in 20 babies are born on their exact due date, and a full-term birth can happen any time between 37 and 42 weeks. Your doctor may adjust the date after an ultrasound.
- What if I have an irregular cycle?
- If your cycles vary, enter your average cycle length for a closer estimate. Calculations based on a last period are less precise with irregular cycles, so an early ultrasound usually gives the most accurate dating.
- Can I calculate from my conception or IVF date?
- Yes. Switch the method to conception date and enter the day you conceived. For IVF, your clinic can give you a precise date based on your transfer.