Pregnancy Due Date Calculator
Enter the first day of your last menstrual period (LMP) to estimate your due date (EDD), how far along you are, and when each trimester ends.
Updated
For general information only — not medical advice. Consult a doctor or registered dietitian before making health decisions.
Formula
Due date = LMP + 280 days (40 weeks)
Adjusted for cycle length: + (cycle − 28) days
This is Naegele's rule, the same method doctors use at the first visit. An early ultrasound scan may revise the date.
Examples
LMP 1 March 2026, 28-day cycle
Estimated due date: 6 December 2026 (Sunday)
LMP 10 June 2026, 32-day cycle
Estimated due date: 21 March 2027 (Sunday)
Important information
- Pregnancy weeks are counted from the LMP, about two weeks before conception — so at conception you are already '2 weeks pregnant'.
- A full-term baby is born between 37 and 42 weeks. Only around 4–5% arrive exactly on the due date.
Frequently asked questions
How is the due date calculated?
By adding 280 days to the first day of your last period, adjusted if your cycle is longer or shorter than 28 days.
How accurate is it?
It's an estimate. Most babies arrive within two weeks either side of the date.
What if I don't know my last period date?
An ultrasound in the first trimester gives the most accurate dating — ask your doctor or LHV.
How many weeks are in each trimester?
First: weeks 1–13, second: 14–27, third: 28 until birth.
Learn more
- Pregnancy Due Date: How It Is Calculated — How doctors estimate your due date from your last period, why pregnancy is counted as 40 weeks, how cycle length changes it, and what the trimesters mean.
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