Pregnancy Week

Pregnancy Week Calculator by Due Date

Enter your due date, LMP, or conception date to see how many weeks pregnant you are today — week by week, with your trimester and days remaining.

How pregnancy weeks are counted

Pregnancy weeks are commonly counted from the first day of the last menstrual period. If you know a due date or conception/ovulation date, the calculator converts that into an equivalent LMP reference.

LMP method: the first day of the last period is week 0 day 0.
Conception method: an equivalent LMP is usually about 14 days earlier.
Due date method: estimated LMP is 280 days before due date.

Medical note

Cycle length, ovulation timing, and ultrasound findings can affect pregnancy dating. Use this as an organizing reference.

Enter a date

Your current pregnancy week will appear here.

Current week

Days pregnant

Estimated due date

Trimester

Days remaining

How to use this as a due date calculator, week by week

This tool works in both directions. If you already know your due date, choose Known due date and it shows exactly how many weeks pregnant you are today — handy when an app or your provider gave you a due date but not your current week.

How many weeks pregnant am I by due date?

Your due date is set at 40 weeks, so the calculator counts back 280 days to your start reference and works out today's week and day (for example, 24+3). It refreshes every day, so you always see your current week without counting by hand.

Week by week and trimester at a glance

Weeks 1–13: first trimester.
Weeks 14–27: second trimester.
Weeks 28–40: third trimester; term is 37 weeks.

For what changes each week, see the pregnancy week guide; to learn how dates are estimated, read how many weeks pregnant am I and weeks to months explained.