Last updated: March 2026
What Is the Pregnancy Due Date Calculator?
Calculate your estimated due date using three methods: last menstrual period (Naegele's rule: LMP + 280 days), conception date (+266 days), or IVF transfer date. See your current week, trimester, and a fun baby size comparison for each week — from a poppy seed to a watermelon.
This tool provides estimates only. Always consult your healthcare provider for medical advice about your pregnancy.
Frequently Asked Questions
How accurate is the due date?
Only about 5% of babies are born on their exact due date. Most arrive within 2 weeks before or after. The estimate uses Naegele's rule (LMP + 280 days).
What is Naegele's rule?
The standard medical formula: add 280 days (40 weeks) to the first day of your last menstrual period. It assumes a 28-day cycle.
Can I use my conception date instead?
Yes. The calculator supports 3 methods: last menstrual period, conception date (+266 days), and IVF transfer date.
What are the baby size comparisons?
Each week of pregnancy includes a fun size comparison — from a poppy seed at 4 weeks to a watermelon at 40 weeks.