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Date & Time
Due Date Calculator
The standard due date is forty weeks from the first day of the last menstrual period, known as Naegeleโs rule. Because it assumes a twenty-eight day cycle, the date shifts for longer or shorter cycles, which is why an early scan is more accurate.
How it works
First day of last period
Average cycle length
Today
Estimated due date
Gestational age today
Gestational age
Estimated conception
Second trimester starts
Third trimester starts
Days remaining
Weeks remaining
Frequently asked questions
How do I use the Due Date Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.