Pregnancy Due Date Calculator (Naegele’s Rule)
Estimate your pregnancy due date from your last menstrual period, and see how many weeks along you are. An estimate, not medical advice. In your browser.
Choose the first day of your last menstrual period.
🔒 Calculated in your browser — nothing is uploaded. Naegele's rule (LMP + 280 days), assuming a 28-day cycle. An estimate only; an ultrasound date from your provider may differ, and this is not medical advice.
Estimate your due date
Pick the first day of your last menstrual period (LMP). The tool adds 280 days (Naegele’s rule) for an estimated due date and shows how many weeks and days along you are, plus the trimester. It assumes a regular 28-day cycle.
An estimate only
This is a rough estimate, not a diagnosis. A dating ultrasound from your healthcare provider is more accurate, especially with irregular cycles, and only about 1 in 20 babies arrive on the exact due date. This tool is for general information and is not medical advice. Your inputs never leave your device.
Frequently asked questions
How is a due date calculated?
Naegele’s rule adds 280 days (40 weeks) to the first day of your last period, assuming a 28-day cycle. Ultrasound dating can adjust it.
How accurate is the due date?
It’s an estimate — most births happen within two weeks either side, and only around 5% land on the exact date. Your provider’s scan is the reference.