Pregnancy Due Date Calculator
Find out when your baby is due. This calculator estimates your due date, conception date, current pregnancy week, and trimester based on the first day of your last menstrual period (LMP).
Pregnancy Due Date Calculator
health calculator
How It Works
Pregnancy is dated from the first day of your last period, not conception. The standard calculation adds 280 days (40 weeks). We adjust for cycle lengths longer or shorter than 28 days. This is an estimate — only about 5% of babies arrive on their exact due date.
Formula
Naegele's Rule: Due Date = LMP + 280 days (40 weeks), adjusted for cycle length
Examples
LMP January 1, 28-day cycle
A last period on January 1 gives a due date around October 8.
Frequently Asked Questions
How is the due date calculated?
We use Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle differs from 28 days, we adjust accordingly.
How accurate is a due date?
Due dates are estimates. Only about 5% of babies are born on their exact due date. Most arrive within two weeks before or after. An ultrasound dating scan is more precise.
Is this calculation a substitute for medical advice?
No. This is an estimate for informational purposes. Always confirm your due date with your doctor or midwife, who can use ultrasound for greater accuracy.
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