Pregnancy Due Date Calculator
Estimates a pregnancy due date from the first day of your last period.
Lilu Baba's Pregnancy Due Date Calculator applies Naegele's rule — adding 280 days to your last period's start date — for a quick estimate. This is informational only; always confirm with your doctor or a dating ultrasound.
How to use this calculator
- Enter the first day of your last menstrual period.
- Your estimated due date (using Naegele's rule, +280 days) updates instantly.
Estimated Due Date
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FAQ
Pregnancy Due Date Calculator — frequently asked questions
It's a widely-used general estimate — only about 5% of babies arrive exactly on the calculated date. A doctor's ultrasound dating is more precise.
A standard method estimating due date as 280 days (40 weeks) after the first day of the last menstrual period, assuming a typical 28-day cycle.