CalKit

Pregnancy Week Calculator

Check current pregnancy week and weekly milestones.

Overview

Calculate your current gestational age (weeks and days) based on your last menstrual period (LMP) or estimated due date. This tool also provides fetal development milestones and maternal changes for each week. Please confirm your gestational age with your healthcare provider via ultrasound.

Formula

Gestational weeks = (Today - LMP) / 7
Gestational days = Today - LMP

Reverse from due date: Gestational days = 280 - (EDD - Today)

How to Use

  1. 1Choose to enter either your LMP or estimated due date.
  2. 2Enter the date.
  3. 3Click the 'Calculate' button.
  4. 4Your current gestational age (X weeks Y days), trimester, and days remaining will be displayed.

Tips

  • ✔Gestational age counts from the first day of the LMP, not from conception.
  • ✔Trimesters are divided as: 1st (weeks 1–12), 2nd (weeks 13–27), 3rd (weeks 28–40).
  • ✔If the ultrasound-based gestational age at 8–12 weeks differs from the LMP-based age by more than 1 week, the ultrasound estimate is preferred.
  • ✔This calculator is for reference only and does not replace medical advice.

FAQ

Q. When does the pregnancy week count start?

Gestational age starts from the first day of the last menstrual period (LMP), counted as week 0, day 0. This means conception typically occurs around week 2. This is the internationally standardized obstetric dating method.

Q. What are trimesters?

Pregnancy is divided into three trimesters. The 1st trimester (weeks 1–12) involves major organ formation. The 2nd trimester (weeks 13–27) sees rapid growth and the start of fetal movement. The 3rd trimester (weeks 28–40) is when the baby prepares for birth.

Q. Can I calculate weeks from my due date?

Yes. By subtracting the remaining days from 280, you can determine the elapsed gestational days and convert them to weeks and days.

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