Use this free online pregnancy due date calculator to estimate your baby's arrival date using Naegele's rule. Simply enter the first day of your last menstrual period to see your estimated due date along with how many weeks and days pregnant you currently are. This tool is for general informational purposes only and is not a substitute for advice from your doctor or midwife.
How to Use the Pregnancy Due Date Calculator
Enter the first day of your last menstrual period in the "First Day of Last Menstrual Period" field.
Select your average cycle length (default is 28 days).
Click "Calculate Due Date" to see your estimated due date.
Review your gestational age, trimester, days to go, and end of 1st trimester date shown in the result.
Frequently Asked Questions
This calculator applies Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP) to estimate your due date.
The calculator requires a valid LMP date that is not in the future. If the field is empty, contains an invalid date, or the date is later than today, it shows an error message instead of a due date.
The estimate uses the cycle length you select (28 days by default) and is a general guideline only - only about 5% of babies are born exactly on their due date. Your healthcare provider may adjust the date based on ultrasound measurements.
Yes, it's completely free to use. However, it's intended for general informational purposes only and should not replace guidance from your doctor or midwife.