Pregnancy Due Date Calculator

This pregnancy calculator estimates your due date based on your last menstrual period (LMP) or conception date. It also provides a timeline of important pregnancy milestones and fetal development stages.

The average cycle is 28 days, but can range from 21 to 45 days.

How the Pregnancy Calculator Works

This calculator uses several methods to estimate your due date:

Naegele's Rule (LMP Method)

The most common method for calculating the due date is Naegele's rule:

Due Date = First day of LMP + 280 days (40 weeks)

This formula assumes a 28-day menstrual cycle. For different cycle lengths, the formula is adjusted:

Due Date = First day of LMP + 280 days + (Cycle Length - 28 days)

Conception Date Method

If you know the conception date:

Due Date = Conception Date + 266 days (38 weeks)

Ultrasound Method

Based on measurements taken during an ultrasound:

Due Date = Ultrasound Date + (280 days - Gestational Age in days at ultrasound)

Pregnancy Timeline

  • First Trimester: Weeks 1-13 (Months 1-3)
  • Second Trimester: Weeks 14-26 (Months 4-6)
  • Third Trimester: Weeks 27-40 (Months 7-9)

It's important to note that pregnancy dating can be complex and may be adjusted based on ultrasound findings or other clinical factors. This calculator provides estimates based on standard formulas. Always consult with your healthcare provider for personalized medical advice.