Pregnancy Due Date Calculator
Estimate your due date, current gestational age and trimester from the first day of your last period.
Estimate your due date
Enter the first day of your last menstrual period (LMP).
Result
Formula used
Due date = LMP + 280 days
This is Naegele's rule, adjusted by a few days if your average cycle is longer or shorter than 28 days.
How to use this calculator
- Enter the first day of your last menstrual period.
- Optionally enter your average cycle length — otherwise 28 days is assumed.
- Press Calculate to see your estimated due date and gestational age.
This tool provides general informational estimates only and is not a substitute for medical advice. Always confirm your due date with a doctor or midwife.
FAQ
Frequently asked questions
How is the due date calculated?
Using Naegele's rule: 280 days (40 weeks) are added to the first day of your last menstrual period, adjusted if your average cycle is longer or shorter than 28 days.
How accurate is this estimate?
It's a statistical estimate — only about 1 in 20 babies arrive exactly on the predicted due date. A first-trimester ultrasound gives a more precise estimate.
What is the estimated conception date?
Conception typically occurs around 14 days after the first day of your last period, adjusted for your cycle length.
Is this medical advice?
No. This tool is for general informational purposes only and does not replace advice from a doctor or midwife.