How is my due date calculated?

The calculator uses the first day of your last menstrual period (LMP) and adds 280 days (40 weeks) to estimate your due date. This is the standard Naegele's rule, assuming a regular 28-day cycle.

Can I find out my conception date?

Yes, the calculator estimates your conception date by subtracting 266 days (38 weeks) from your due date, which is the average time from conception to birth. This is an estimate, as conception can vary by a few days.

What if my cycle is irregular?

The calculator assumes a regular 28-day cycle. If your cycle is longer or shorter, your due date may differ. For the most accurate estimate, consult your healthcare provider, who may use ultrasound measurements.

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即时、私密且免费

预产期计算器.

2026年8月4日

根据末次月经计算预计产期

此计算器尚未完全翻译——部分文本以英文显示。

设备端计算无需注册

输入数值

输入时结果会更新。

02 / 答案

末次月经

输入您末次月经的第一天。此估算假设为规律的28天周期和280天孕期。

末次月经第一天

注意: 这只是一个估算值，而非精确预测。只有少数分娩会恰好发生在预产期当天，医生可以通过超声波检查给出更准确的日期。

预计预产期

August 18, 2027

280 剩余天数

当前进度

0w 0d

孕期阶段

1st

进度0%

预计受孕日期: ~11/25/2026

已过时间: 0 周

下一个里程碑: 进入孕中期

Cite this calculator

Canonical URL: https://mathify.one/zh/health/due-date

Updated 2026年8月4日

Cite as: Mathify. (2026). 预产期计算器. https://mathify.one/zh/health/due-date

Use Cases

Plan for your baby's arrival

Know your estimated due date to plan maternity leave, prepare the nursery, and schedule prenatal appointments.

Example: Enter your LMP to see your due date and current pregnancy week.

Track pregnancy progress

Monitor how far along you are and what to expect each week, helping you stay informed about your baby's development.

Example: At 20 weeks, you're halfway through your pregnancy.

Frequently Asked Questions

How is my due date calculated?: The calculator uses the first day of your last menstrual period (LMP) and adds 280 days (40 weeks) to estimate your due date. This is the standard Naegele's rule, assuming a regular 28-day cycle.
Can I find out my conception date?: Yes, the calculator estimates your conception date by subtracting 266 days (38 weeks) from your due date, which is the average time from conception to birth. This is an estimate, as conception can vary by a few days.
What if my cycle is irregular?: The calculator assumes a regular 28-day cycle. If your cycle is longer or shorter, your due date may differ. For the most accurate estimate, consult your healthcare provider, who may use ultrasound measurements.

Tips & Common Mistakes

Tips

Enter the first day of your last menstrual period accurately for the best estimate.
Remember that only about 5% of babies are born on their exact due date; it's normal to give birth a week or two before or after.
Use the conception date estimate to understand your pregnancy timeline, but rely on ultrasound for precise dating.
If your cycle is longer than 28 days, your due date may be later; consider discussing with your doctor.

Common Mistakes to Avoid

Using the date your period ended instead of the first day of your last period.
Assuming the due date is exact; it's an estimate and can change based on ultrasound findings.
Forgetting to account for irregular cycles, which can affect the accuracy of the calculation.

Last updated: August 13, 2026