Due Date Calculator
Estimate a due date and current week from your last period.
An estimated due date
The most common way to estimate a due date is Naegele’s rule: add 280 days, or forty weeks, to the first day of the last menstrual period. This tool does that and shows how far along the pregnancy is today.
It reports the estimated due date, the current week and day of gestation, and which trimester that falls in. A dating ultrasound refines the estimate, but this is the standard starting point.
Supportive and private
It applies the 280-day rule in your browser, so this personal date is never uploaded.
Frequently Asked Questions
How is the due date found?
Naegele’s rule adds 280 days — 40 weeks — to the first day of your last menstrual period. It assumes a regular 28-day cycle.
How accurate is it?
It is the standard estimate, but only about one in twenty births lands exactly on it. A dating scan gives a more precise date.
Is my information private?
Yes. The date you enter is used only in your browser and never uploaded.
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