🤰 Due Date Calculator
Calculate estimated pregnancy due date
How Due Date Calculation Works
Formula
Due Date = LMP + 280 days (40 weeks)
- 1Enter the first day of your last menstrual period (LMP).
- 2The calculator adds 280 days (40 weeks) to the LMP date.
- 3This is Naegele's rule, the standard method used by doctors.
- 4Alternatively, enter a known conception date and add 266 days.
- 5The result includes your current week, trimester, and estimated due date.
About Due Date Calculator
Calculate your estimated pregnancy due date based on last menstrual period, conception date, or IVF transfer date. Get week-by-week pregnancy timeline and trimester breakdown.
Frequently Asked Questions
How accurate is the due date calculator?
Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after. The due date is an estimate, not a guarantee.
What is Naegele's rule?
Naegele's rule estimates the due date by adding 280 days (40 weeks) to the first day of the last menstrual period. It assumes a 28-day cycle with ovulation on day 14.
Can my due date change?
Yes. Ultrasound measurements, especially in the first trimester, may adjust your due date if the baby's size doesn't match the LMP-based estimate.