How many weeks pregnant am I? How pregnancy weeks are counted

Short answer: count the days from the first day of your last period to today, then divide by 7. The whole weeks are your pregnancy week and the remainder is the day — for example 171 days is 24 weeks 3 days.

1. The starting point is your last period, not conception

Doctors and midwives date a pregnancy from the first day of the last menstrual period (LMP). Conception usually happens about two weeks later, which is why you are already “4 weeks pregnant” when a test turns positive.

2. A full pregnancy is about 40 weeks (280 days)

Your estimated due date is LMP + 280 days. Only a small share of babies arrive exactly on that day; anywhere from 37 to 42 weeks is common.

3. Trimesters

First trimester: weeks 1–13. Second trimester: weeks 14–27. Third trimester: week 28 until birth.

4. If your scan gave a different date

An early ultrasound measures the baby and may move your due date. Use the date your care provider gives you from then on.

Doing this with Ninemoon

Enter your due date, your last period or the weeks from your scan once. Ninemoon then shows your week and day every morning, the countdown to your due date, and every date in the calendar with its week — no counting on your fingers.

FAQ

Get Ninemoon, the no-sign-up pregnancy calendar (Google Play)

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