Due Date Calculator
Calculate your estimated due date based on last menstrual period
About this calculator
A due date calculator estimates your baby's expected arrival date based on your last menstrual period (LMP). This tool uses the standard 280-day pregnancy calculation, adding 40 weeks to the first day of your last period. It's essential for tracking pregnancy milestones, scheduling prenatal appointments, and preparing for your baby's arrival. Healthcare providers use this same method to establish your estimated due date and monitor fetal development throughout pregnancy.
How to use
Enter the first day of your last menstrual period in the date field. The calculator will automatically add 280 days (40 weeks) to determine your estimated due date. Make sure to use the correct date format and double-check your LMP date for accuracy.
Frequently asked questions
How accurate is the due date calculator?
The calculator provides an estimate with about 80% accuracy. Only 5% of babies are born exactly on their due date, with most arriving within two weeks before or after.
What if I have irregular periods?
The calculator may be less accurate with irregular cycles. Consult your healthcare provider who may use ultrasound dating for a more precise estimate.
Can the due date change during pregnancy?
Yes, your doctor may adjust the due date based on ultrasound measurements, especially if they differ significantly from the LMP-based calculation.