Pregnancy Due Date Calculator
Estimate a due date and current gestational age from the first day of your last menstrual period.
Your details
Enter only the information needed for this estimate.
Complete the fields and select “Estimate my due date” to see your estimate.
Your estimated due date
A due date is a reference point for pregnancy care, not a prediction of the exact birth date.
Your clinician may confirm or revise dating after reviewing your history and ultrasound measurements.
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How the date is estimated
Pregnancy dating convention counts 280 days, or 40 weeks, from the first day of the last menstrual period for a 28-day cycle. The calculator adjusts that estimate when you enter a different usual cycle length.
This approach assumes the menstrual date is known and the cycle pattern is reasonably regular. It is less dependable when either assumption does not fit.
Why a date may change
Early ultrasound measurements can provide important dating information. Clinicians consider the menstrual history, assisted reproduction dates when relevant, and ultrasound findings before establishing the due date used for care.
Once an estimated due date has been established, changes are generally reserved for specific circumstances. Use the date documented by your maternity team for decisions and appointments.
Limits of this estimate
- Irregular cycles, uncertain bleeding dates, recent hormonal contraception, breastfeeding, or postpartum cycles can reduce the usefulness of a period-based estimate.
- The result does not confirm pregnancy or determine when conception occurred.
- An estimated due date cannot predict the day labor will begin.
Common questions
How should I use this estimate?
Use it as a planning starting point, then compare it with your own experience and any guidance from a qualified health professional.
Is this medical advice?
This calculator provides a general educational estimate only. It does not confirm or date a pregnancy for clinical care and does not replace advice from your maternity professional.
What happens to what I enter?
The calculator uses the values in your current browser session to produce the result. It does not save them in browser storage.