How many weeks and days are you pregnant for?

“How many days are you pregnant for?” sounds like it should have one tidy answer — and it roughly does, once you know which clock is being used. The standard figure is about 280 days, or 40 weeks, counted from the first day of your last period.

The headline numbers

• 280 days from the first day of the last menstrual period to the due date.
• 40 weeks — the same span expressed in weeks.
• About 266 days (38 weeks) if you count from conception instead, which happens roughly two weeks after the last period.

So the answer depends on the starting line. Clinicians count from the last period, which is why pregnancy is described as 40 weeks even though it’s about 38 weeks from conception. The reasoning is in gestational age vs. fetal age.

How many months is that?

Forty weeks is a little over nine calendar months — not exactly nine, because months are longer than four weeks. That mismatch is why pregnancy is tracked in weeks, which are precise, rather than months, which vary in length. Nine months is a friendly approximation; 40 weeks is the working figure.

What counts as “full term”?

Full term isn’t a single day. ACOG defines full term as 39 0/7 to 40 6/7 weeks, with early term (37–38 weeks), late term (41 weeks) and post-term (42 weeks and beyond) around it. Most births land in a window around the due date rather than on it. The milestones are mapped in pregnancy trimesters and milestones.

“When am I due?” — finding your own number

To turn these general figures into your own dates, you need one known date. From your last period, the due date is that date plus 280 days — the due date calculator does it instantly. To see exactly how far along you are today in weeks and days, use the gestational age calculator. If you know your ovulation or conception date instead, the conception date calculator counts 266 days forward.

Why your due date is only an estimate

However it’s calculated, a due date is a reference point, not a deadline — births naturally spread across roughly a month around it, and only a small share happen exactly on the date. A first-trimester ultrasound is the most accurate way to pin it down; see how accurate is your due date.