Pregnancy Due Date Calculator
Calculate your due date by LMP, conception date, IVF embryo transfer (Day 3/5), or ultrasound. Shows gestational age, trimesters, pregnancy milestones, and weekly baby size comparisons.
How to use
- 1Choose your calculation method: LMP, Conception Date, IVF Transfer, or Ultrasound
- 2Enter the relevant date and required parameters
- 3View your due date, current gestational age, and trimester
- 4Explore key pregnancy milestones and weekly baby size comparisons
Frequently Asked Questions — Pregnancy Due Date Calculator
What is Naegele's rule?+
Naegele's rule, proposed by Dr. Franz Karl Naegele in 1812, is the most widely used method for estimating due dates. Formula: Due Date = First day of LMP + 9 months + 7 days (or + 280 days). This assumes a 28-day cycle with ovulation on day 14. If your cycle differs, the due date is adjusted accordingly.
Can the due date change?+
Your initial due date may be revised after an ultrasound, especially a first-trimester scan (weeks 8–12), which is the most accurate way to determine gestational age. Only about 4% of babies are born on their due date; most arrive within 2 weeks before or after.
Why do LMP and ultrasound due dates differ?+
LMP-based dates assume a 28-day cycle with ovulation on day 14. In reality, cycle lengths vary, so actual ovulation and conception dates differ too. Ultrasound measures fetal size directly to estimate gestational age more accurately, especially when performed in the first trimester.
How does IVF due date calculation work for Day 3 vs Day 5?+
In IVF, embryos are cultured in a lab before transfer. A Day 3 embryo (cleavage stage) equates to day 17 of a natural cycle, while a Day 5 blastocyst equates to day 19. The due date is calculated as: Transfer Date + (266 − embryo age in days) days. This tool automatically adjusts for your chosen transfer day.