Estimate a pregnancy due date
Estimate a pregnancy due date and current week from the first day of the last menstrual period.
Based on Naegele's rule (last period + 280 days) assuming a standard 28-day cycle. An estimate only. Only about 5% of babies arrive on their exact due date, and an ultrasound-based estimate from a healthcare provider is more accurate than this calculation.
The start date of your last menstrual period (LMP).
The standard estimate, based on a typical 28-day cycle.
Along with the estimated due date and days remaining.
Frequently asked
How is the due date calculated?
Naegele's rule: the first day of your last menstrual period, plus 280 days (40 weeks). The standard estimate assuming a typical 28-day cycle. It's a starting point, not a guarantee.
How accurate is this estimate?
Only around 5% of babies are born on their exact due date, and cycles that are longer or shorter than 28 days shift the real due date earlier or later than this calculation. An ultrasound-based estimate from a healthcare provider is more accurate.
What are the trimesters?
1st trimester is weeks 0-13, 2nd trimester is weeks 14-27, and 3rd trimester is weeks 28-42, based on the current gestational week from your LMP.
Is this medical advice?
No. This is a mathematical estimate for general informational purposes only, not medical advice. Please confirm your due date and any pregnancy-related concerns with a doctor or midwife.