Pregnancy calculator: how many weeks pregnant am I?
Enter the first day of your last period (or your due date) to see exactly how far along you are, which trimester you're in and what's coming up next.
Don't know either? Use the due date calculator with a conception, IVF or scan date.
Enter a date to see how far along you are.
How gestational age is counted
Midwives and doctors count pregnancy in completed weeks and days from the first day of your last menstrual period. That's why you are already "4 weeks pregnant" when a test first turns positive, only about two weeks after conception. A term pregnancy is 37+0 to 41+6 weeks, and full term (the best outcomes for babies) is 39+0 to 40+6, according to ACOG's 2013 definitions.
The due date calculator has an interactive walkthrough of why the count starts two weeks before conception.
| Trimester | Weeks | Months (approx.) |
|---|---|---|
| First | 1 – 13+6 | 1 – 3 |
| Second | 14 – 27+6 | 4 – 6 |
| Third | 28 – birth | 7 – 9 |
Frequently asked questions
How many weeks pregnant am I?
Count from the first day of your last period, not from conception. If your last period started 8 weeks ago today, you are 8 weeks pregnant, even though conception happened about 6 weeks ago. The calculator above does this count for you, including days.
What does "12+3" mean?
It is shorthand for 12 weeks and 3 days of gestation. Clinicians write gestational age this way on scan reports and in maternity notes.
When does each trimester start?
The first trimester runs from week 1 to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth. Some sources split them slightly differently (e.g. 12 and 26 weeks), so don't worry if your app disagrees by a week.
How many months pregnant is 20 weeks?
About 4.5 months. Because months have 4.3 weeks on average, 40 weeks is a little over 9 calendar months. A common mapping is: months 1–3 = weeks 1–13, months 4–6 = weeks 14–27, months 7–9 = weeks 28–40.