How Many Weeks Pregnant Am I? Weeks, Days and Trimesters Explained

Doctors count pregnancy from the first day of the last menstrual period (LMP), not from conception. So you are "four weeks pregnant" around the time a period is missed, even though conception happened about two weeks earlier.

Quick answer

Enter the first day of your last period. The tool shows how many weeks and days pregnant you are, the trimester, the due date (280 days from that date) and the days left.

Worked example

If your last period began 100 days ago:

• 100 days ÷ 7 = 14 weeks and 2 days.
• You are in the second trimester.
• Days left until the due date: 180.

Trimesters

• First trimester: weeks 1 to 13. Early development, often tiredness and nausea.
• Second trimester: weeks 14 to 27. Many people feel better and may feel movements.
• Third trimester: weeks 28 to 40. Growth and preparation for birth.

Steps

1. Enter the LMP date.
2. Read the week, day and trimester.

Good to know

• A pregnancy scan may give a different number if cycles are irregular; doctors then follow the scan date.
• "Weeks pregnant" and "weeks since conception" differ by about two weeks.
• Different apps may show "week 14" as having completed 13 weeks; this tool states weeks completed plus days.

Health note

Book your first antenatal appointment early and follow your local guidelines for scans and tests. This tool is for information, not medical advice.