1. What is the Pregnancy Due Date Calculator?

The pregnancy due date calculator estimates the expected delivery date based on the first day of your last menstrual period (LMP). This calculation uses Naegele's rule which adds 280 days (40 weeks) to the LMP.

2. How Does the Calculator Work?

The calculator uses the standard formula:

Where:

• LMP — First day of last menstrual period
• 280 days — Equivalent to 40 weeks gestation

Explanation: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The calculator also shows current gestational age in weeks and days.

3. Importance of Due Date Calculation

Details: Knowing your estimated due date helps healthcare providers monitor fetal development, schedule important tests, and determine if the pregnancy is progressing normally.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the format YYYY-MM-DD. The calculator will display your estimated due date and current gestational age.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this due date calculation?
A: Only about 5% of women deliver on their exact due date. Most deliver within 2 weeks before or after.

Q2: What if my cycles aren't 28 days?
A: For irregular cycles, an ultrasound dating scan in the first trimester provides more accurate dating.

Q3: Why 280 days if pregnancy is 9 months?
A: Pregnancy is actually about 9.5 lunar months (4 weeks each). 280 days equals 40 weeks.

Q4: When will my provider adjust my due date?
A: If first-trimester ultrasound differs by >5 days from LMP date, providers typically use the ultrasound date.

Q5: What's considered full term?
A: Between 37 weeks 0 days and 41 weeks 6 days. Earlier is preterm, later is postterm.