Pregnancy Due Date Calculator
Calculate your estimated due date based on LMP and average cycle length.
Due Date Estimator
About Due Date Estimation
Due date estimation helps predict when a baby is likely to be born, typically around40 weeks (280 days) from the first day of the mother’s last menstrual period (LMP). This calculation assumes a regular 28-day menstrual cycle, where ovulation occurs approximately 14 days after the cycle begins. For women with shorter or longer cycles, adjustments are made to improve accuracy.
Calculation Methods
- Naegele’s Rule: Adds 280 days (or 9 months + 7 days) to the LMP.
- Cycle Adjustment: For non-28-day cycles, the due date is modified based on ovulation timing.
- Ultrasound Dating: Early ultrasounds (before 14 weeks) provide more accurate gestational age estimates.
- Conception Date Method: Adds 266 days (38 weeks) from the actual date of conception.
- IVF Calculation: Based on the exact date of embryo transfer or fertilization.
Important Facts
- Pregnancy is divided into three trimesters, each lasting about 13 weeks.
- Only about 5% of babies are born exactly on their estimated due date.
- Ultrasound dating is most reliable in the first trimester.
- Factors like cycle irregularity or implantation timing can affect accuracy.
- The estimated due date marks 40 weeks of gestation — not conception.
Due date estimation serves as a valuable guideline for tracking fetal growth, planning prenatal visits, and preparing for delivery. However, it’s important to remember that it’s an estimate — natural variations mean that most healthy pregnancies reach full term between 37 and 42 weeks. Regular checkups help ensure the most accurate monitoring throughout pregnancy.