How Many Weeks Pregnant Am I? Due Date Math | AgeGapCalc
Pregnancy is measured in weeks from the first day of the last menstrual period, with a typical full term near 40 weeks.
Our calculator converts between a due date and current date to show how many weeks along you are.
Weeks From Last Period
Pregnancy is dated from the first day of the last menstrual period, not from conception, which is why the count starts about two weeks before conception actually occurs.
Due Date Backwards
A due date is a countdown of 40 weeks from that starting point, so weeks pregnant can equally be worked out backwards from the due date.
A Math Aid, Not Medical Advice
The calculator reproduces the standard arithmetic; it does not assess a pregnancy. Always follow the dates given by a clinician, which may be adjusted after a scan.
Why the Dating Convention Matters
Because the starting point is the last period rather than conception, being six weeks pregnant means about four weeks after conception. Knowing the convention prevents confusion when comparing dates from different sources.
Gestational age is the clinical term for this count, and it is the figure that appears on scan reports.
Common Confusions Explained
The most common confusion is comparing a weeks-pregnant figure with the number of weeks since conception. The clinical count runs about two weeks ahead, because it begins at the last period.
The second is treating 40 weeks as an exact due date. It is a reference point, and clinicians routinely revise it after an early scan.
Open the Date Duration Calculator to measure any span.
Open the Date Duration Calculator →Frequently Asked Questions
How long is a full-term pregnancy?
About 40 weeks from the last period.
Can I use my due date?
Yes, the tool converts between due date and today.
Is it exact?
It is exact date math, but only a guide.
Should I trust it medically?
No, confirm with your provider.
Leap years?
Handled.
Is the information I enter kept confidential?
Yes.
How do I convert weeks pregnant into months?
Pregnancy months are counted as roughly 4.3 weeks, so 40 weeks works out to about nine calendar months rather than ten.
Can I work out the conception date from this?
Only roughly: subtract about two weeks from the gestational age. A clinician can date a pregnancy more accurately from a scan.
Why is the count higher than the weeks since conception?
Because pregnancy is dated from the first day of the last period, which is around two weeks before conception happens.