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Pregnancy Due Date
🤰 Pregnancy Due Date Calculator
Estimate your due date and current week of pregnancy from the first day of your last menstrual period (LMP) — the standard method used by most clinicians for an initial estimate.
This uses Naegele's Rule: due date ≈ LMP + 280 days, adjusted for cycles longer or shorter than the standard 28 days. It assumes ovulation occurred roughly two weeks after your LMP, which is the most common clinical estimate before an ultrasound provides a more precise date.
Frequently Asked Questions
How accurate is the LMP method?
It's a solid first estimate, but only about 4% of babies arrive on the exact calculated date — a first-trimester ultrasound dating scan is more precise and is what most doctors rely on after the initial estimate.
What if I have irregular cycles?
The cycle-length adjustment helps, but very irregular cycles make LMP dating less reliable — an early ultrasound is the better option in that case.
What do the three trimesters mean?
Roughly weeks 1–13 (1st), 14–27 (2nd), and 28–40+ (3rd) — each associated with different stages of fetal development and different routine prenatal checks.
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