Estimate your due date and exactly how many weeks and days pregnant you are — based on your last period or your conception date.
Pregnancy is conventionally counted in weeks starting from the first day of your last menstrual period (LMP), not from the date of conception — even though conception typically happens about two weeks after that. That's why "6 weeks pregnant" usually means about 4 weeks since conception.
The standard method for estimating a due date is Naegele's rule: add 280 days (40 weeks) to the first day of your last period. If your average cycle is longer or shorter than 28 days, this calculator adjusts the estimate accordingly, since ovulation shifts earlier or later with cycle length.
If you know your conception date instead (for example, from fertility tracking or IVF), the calculator adds 266 days (38 weeks) directly from that date.
Only around 4–5% of babies are actually born on their exact estimated due date. Naegele's rule gives a reasonable starting estimate, but an ultrasound dating scan in the first trimester is generally more accurate, especially for irregular cycles.
The exact date of conception is rarely known with certainty, but the start of the last period usually is — so it became the standard reference point, even though it means "weeks pregnant" runs about two weeks ahead of time since conception.
This calculator's cycle-length adjustment helps, but irregular cycles make LMP-based estimates less reliable generally. An early ultrasound is the more accurate option if your cycles vary significantly.
First trimester: weeks 1–13. Second trimester: weeks 14–27. Third trimester: week 28 to birth, typically around week 40.
No. This calculator estimates dates from information you already have (your last period or conception date) — it doesn't detect or confirm pregnancy. A home pregnancy test or a healthcare provider can do that.