预产期计算器(内格勒法) — 公式

Naegele's Rule

The estimated due date is 280 days (40 weeks) from the first day of the last menstrual period (LMP).

Due Date = LMP + 280 days

Trimester Breakdown

TrimesterWeeks First1-12 Second13-27 Third28-40

Only about 5% of babies are born on their exact due date. Most arrive within 2 weeks of the estimate.

计算示例

A woman whose last period started 84 days ago.

  1. Gestational week = floor(84 / 7) = 12 weeks
  2. Extra days = 84 - 12 x 7 = 0
  3. Days remaining = 280 - 84 = 196 days
  4. Weeks remaining = 196 / 7 = 28.0 weeks