Pregnancy Due Date Calculator
Calculate your pregnancy due date
Calculator
Average is 28 days. Enter your usual cycle length.
How to Use
Calculate your pregnancy due date
Enter last period date
Input the first day of your last menstrual period
Or enter conception date
Alternatively, input your conception/ovulation date
Set cycle length
Adjust if your cycle differs from 28 days
View due date
See estimated due date and pregnancy timeline
Naegele's Rule
Due Date = LMP + 280 days (40 weeks) OR Conception Date + 266 days (38 weeks)
Assumes 28-day cycle with ovulation on day 14. Adjust for longer/shorter cycles.
Frequently Asked Questions
The standard method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). Alternatively, add 266 days from conception date. Due dates are estimates - only 5% of babies are born on their due date.
Due dates are accurate within a 2-week window. 80% of babies are born between 38-42 weeks. First ultrasounds (before 14 weeks) can adjust due date by measuring baby size. Later ultrasounds are less accurate for dating.
Irregular cycles make LMP-based calculation less accurate. An early ultrasound is the best way to establish due date. You can also calculate from ovulation date if known (conception + 266 days), or IVF transfer date for fertility treatments.
First trimester: weeks 1-12 (organ development). Second trimester: weeks 13-26 (growth, movement felt). Third trimester: weeks 27-40 (final growth, preparation for birth). Each trimester has different symptoms and milestones.