Where you are in the 40 weeks
The bands are the three trimesters; the pointer marks your current gestational week.
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Pregnancy
Pregnancy Calculator
Enter the first day of your last menstrual period to find your due date, how many weeks along you are, your trimester, and your estimated conception date.
Estimated due date
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You are—
Trimester—
Conception (approx.)—
Days remaining—
How it works
Pregnancy is dated from the first day of your last menstrual period (LMP), not from conception, because the LMP is easier to pin down. A full-term pregnancy is counted as 280 days (40 weeks) from that date, which is Naegele's rule. Conception typically happens about two weeks after the LMP, around ovulation.
Due date = LMP + 280 days
Conception ≈ LMP + (cycle length − 14) days
Gestational age = today − LMP
Conception ≈ LMP + (cycle length − 14) days
Gestational age = today − LMP
- First trimester: weeks 1–13. Second: weeks 14–27. Third: weeks 28–40.
- Only about 1 in 20 babies arrive on the exact due date; a two-week window either side is normal.
- An early ultrasound gives the most accurate dating and may adjust these estimates.
Frequently asked questions
Why is my due date counted from my last period?
Because the exact day of conception is rarely known, clinicians count from the LMP, a date most people can identify. It adds roughly two weeks compared with dating from conception.
What if my cycle isn't 28 days?
A longer or shorter cycle shifts ovulation and conception, so the calculator adjusts the conception estimate using your cycle length while keeping the standard 280-day due date.