Due Date Calculator

Naegele-style due date from last menstrual period (LMP + 280 days).

Due Date Calculator helps you naegele-style due date from last menstrual period (LMP + 280 days). Enter first day of last period, review the breakdown, and use the guidance below to understand what the number means — and what it does not. What the Due Date calculator does Due Date Calculator is built for body measurements, calories, and everyday health math. Naegele-style due date from last menstrual period (LMP + 280 days). You enter first day of last period, then Simple Calculators computes the result instantly. These tools use widely published formulas. They are educational screens, not a diagnosis. How the math works Enter the First day of last period. The calculator adds 280 days (40 weeks) to get the due date — this is Naegele’s rule. It also estimates conception at 14 days after the period started, counts the weeks and days of pregnancy as of today, and splits the pregnancy into three trimesters. It assumes a regular 28-day cycle. The formula: Due date = first day of last period + 280 days. 280 days is 40 weeks. Assumes a 28-day cycle.