Know your week, trimester, and due date instantly
Enter Your Last Period Date
Use the first day of your last normal period — this is how doctors count gestational age.
Your Pregnancy Summary
gestational age (obstetric week 11)
Pregnancy Milestones
Medical disclaimer: This calculator is for informational purposes only and is not a substitute for professional medical advice. Gestational age is counted from the first day of your last menstrual period (LMP), as used in standard obstetric practice. Your healthcare provider may adjust your due date based on ultrasound measurements. Always consult your doctor or midwife for medical guidance.
The Pregnancy Week Calculator tells you exactly how many weeks pregnant you are, which trimester you are in, and your estimated due date — all from the first day of your last menstrual period (LMP). Doctors count gestational age starting from LMP, making this the same method your healthcare provider uses. Enter your date and get instant, accurate results with key pregnancy milestones.
Pregnancy week (gestational age) is counted from the first day of your last menstrual period (LMP), not from conception. At the start of your LMP you are considered 0 weeks pregnant, so by the time conception occurs around day 14 you are already 2 weeks pregnant by obstetric standards.
The first trimester covers weeks 1–13, the second trimester covers weeks 14–26, and the third trimester runs from week 27 until birth (typically around week 40). These boundaries may vary slightly by source, but the ranges used here match standard obstetric practice.
The estimated due date (EDD) is calculated as 280 days (40 weeks) after your LMP. It is an estimate — only about 5% of babies are born exactly on their due date. Your provider may adjust the EDD based on ultrasound measurements, especially if your cycles are irregular.
If you are unsure of your LMP, your doctor or midwife can estimate gestational age using an early ultrasound (ideally before 14 weeks), which measures the size of the embryo or fetus for a more precise dating.