Pregnancy Due Date Calculator
Calculate your estimated due date, current week, and trimester — free and instant
Calculate Using
First Day of Last Period
Average Cycle Length
How Due Dates Are Calculated
The most common method (Naegele's rule) estimates your due date as 280 days (40 weeks) from the first day of your last menstrual period, assuming a 28-day cycle.
If your cycle is longer or shorter than 28 days, this calculator adjusts the estimate accordingly.
For conception-based calculation, your due date is estimated at 266 days (38 weeks) from the conception date.
Pregnancy Trimesters
First TrimesterWeeks 1-13Early development, morning sickness common
Second TrimesterWeeks 14-27Often called the 'golden period', energy returns
Third TrimesterWeeks 28-40+Final growth, preparation for birth
Important Note
This calculator provides an estimate only. Only about 5% of babies are born exactly on their due date. Always consult your doctor or midwife for accurate dating, especially through ultrasound confirmation.
FAQ
Q: How accurate is a due date calculator?
A: Due date calculators provide an estimate. Only about 5% of babies arrive on the exact predicted date — most arrive within 2 weeks before or after.
Q: What if I don't know my last period date?
A: Use the conception date method instead, or consult your doctor for an ultrasound-based estimate, which is often more accurate.
Q: What is considered full term?
A: Full term is defined as 39 weeks to 40 weeks and 6 days. Babies born before 37 weeks are considered preterm.
Q: How is gestational age different from fetal age?
A: Gestational age is counted from the last menstrual period, while fetal age is counted from conception — gestational age is typically about 2 weeks more.
Q: Can cycle length affect my due date?
A: Yes. Longer or shorter cycles shift when ovulation likely occurred, which this calculator accounts for when you select your cycle length.