Pregnancy Due Date Calculator
Calculate estimated due date and current gestational age using Naegele's Rule (LMP + 280 days) or ultrasound dating.
Results
What is it?
The Pregnancy Due Date Calculator estimates your Expected Due Date (EDD) and current gestational age using Naegele's Rule — the standard clinical method. LMP stands for Last Menstrual Period, and the rule adds 280 days (40 weeks) to that date, adjusted for your personal cycle length. Pregnancy is divided into three trimesters: First (weeks 1-12), Second (weeks 13-26), and Third (weeks 27-40).
How to use
1. Enter the year, month, and day of your Last Menstrual Period (LMP) — the first day of your last period. 2. Enter your average menstrual cycle length (most women are 28 days; range 20-45 days). 3. The calculator shows your gestational age in weeks and which trimester you are in. 4. For the most accurate EDD, always confirm with an ultrasound — particularly a dating scan at 8-12 weeks.
Example scenario
LMP: January 1, 2025. Cycle: 28 days. Naegele's Rule gives EDD approximately October 8, 2025 (280 days later). At 10 weeks gestation, the calculator shows Trimester 1. If cycle were 35 days, the adjusted gestation becomes 287 days.
Pro tip
Ultrasound dating in the first trimester is more accurate than LMP-based calculations, especially if your cycles are irregular. The plus/minus 2-week margin is clinically accepted. Always discuss your EDD with your midwife or OB — it can change as the pregnancy progresses.