How are pregnancy weeks counted?

Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception. Week 1 starts on the LMP date; week 40 is the due date.

What trimester am I in?

First trimester: weeks 1–12. Second trimester: weeks 13–26. Third trimester: weeks 27–40.

Pregnancy Weeks Calculator – How Many Weeks Pregnant?

Pregnancy Weeks Calculator

Find out exactly how many weeks and days pregnant you are from your last menstrual period.

First day of last menstrual period (LMP)

Pregnancy is counted from the first day of your LMP, not from conception. Week 1–2 of pregnancy technically precede ovulation.

Pregnancy Weeks Calculator

The Pregnancy Weeks Calculator tells you exactly how far along you are in your pregnancy based on the first day of your last menstrual period (LMP).

How pregnancy weeks are counted

Clinicians count pregnancy from the LMP, not from fertilisation. A full-term pregnancy is 40 weeks (280 days) from LMP. At conception (approximately week 2), you are already "2 weeks pregnant" by this convention.

Trimester breakdown

First trimester: Weeks 1–12
Second trimester: Weeks 13–27
Third trimester: Weeks 28–40