預產期計算器
計算您的預產期並跟蹤孕期各階段。
預產期
預測寶寶出生日期
本計算器使用內格勒法則（Naegele's Rule），即在末次月經的第一天加上 280 天（40 周）。這是醫療專業人員使用的標準方法。
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Estimating Your Pregnancy Due Date
Overview
A due date estimates when a baby is likely to arrive, typically about 40 weeks from the first day of the last menstrual period. This calculator gives that estimate instantly from your last period date. It is a guide — only a small share of babies arrive exactly on the due date.
How to Use (Step by Step)
- 1
Enter your last period date
Use the first day of your last menstrual period.
- 2
Adjust cycle length if needed
The default assumes a 28-day cycle.
- 3
Read the estimated due date
It also shows roughly how many weeks along you are.
How It Works
The most common method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period, assuming a regular 28-day cycle. The tool can adjust for cycle length. Because conception timing varies, the result is an estimated date, with normal full-term delivery occurring anywhere from 37 to 42 weeks. A healthcare provider can refine it with an ultrasound.
When to Use This
Getting an early estimate of when your baby may arrive. Tracking how many weeks along you are. Planning appointments and leave around an expected date.
Frequently Asked Questions
It is an estimate. Only about 1 in 20 babies arrive on the exact due date; most come within a couple of weeks either side.