Pregnancy Due Date Calculator
Estimate an expected delivery date from the first day of your last menstrual period (LMP) or a known conception date. The result is an estimate and should be confirmed with your antenatal care provider.
Enter pregnancy dating information
Pregnancy Due Date Calculation Results
Calculation methodology
LMP method: expected delivery date = first day of the last menstrual period + 280 days + (cycle length - 28 days). Known conception method: expected delivery date = conception date + 266 days. Gestational age uses the estimated pregnancy start date. All dates are calendar-day estimates.
Ultrasound and clinical assessment can change the estimated due date. A date alone cannot confirm pregnancy, gestational age, fetal health or a safe delivery time.
Frequently asked questions
What is a pregnancy due date?
It is an estimated date of delivery, not a guaranteed birth date.
How is the due date calculated?
For a regular 28-day cycle, add 280 days (40 weeks) to the first day of the last menstrual period.
Can I calculate from a known conception date?
Yes. An estimate is 266 days after the conception date.
What if my cycle is not 28 days?
The menstrual-period method can be adjusted by the difference between your usual cycle length and 28 days, but ultrasound dating may be more reliable.
What if I do not remember my last period?
A clinician can estimate gestational age using ultrasound and other clinical information.
Will my baby arrive on the due date?
Not necessarily. Many births happen before or after the estimated date.
Is this calculator a medical diagnosis?
No. It is an educational estimate and does not replace antenatal care or a clinician-confirmed due date.
Important health information
Seek antenatal care to confirm your dates. If you have severe abdominal pain, heavy bleeding, fainting or other urgent symptoms, seek immediate medical assessment. This calculator does not replace medical advice.