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Pregnancy Due Date Calculator

Due date, pregnancy week and trimester.

Calculate from
days

How to use

  1. 1Choose how to calculate: last period (LMP) or conception date.
  2. 2Enter the date, and your usual cycle length if it isn't 28 days.
  3. 3See your estimated due date, current week and trimester.
  4. 4Check the key milestones listed below.

Frequently asked questions

How is the due date calculated?

Using Naegele's rule: 280 days (40 weeks) after the first day of your last period, adjusted for longer or shorter cycles. From conception, it's 266 days.

How accurate is the due date?

It's an estimate. Only about 1 in 20 babies arrive exactly on the due date; most arrive within two weeks either side. An early ultrasound gives the most accurate date.

Why count from my last period, not conception?

Most people know the date of their last period but not the exact day of conception, so doctors count pregnancy weeks from the period.

What are the trimesters?

First trimester: weeks 1–13, second: weeks 14–27, third: week 28 until birth.

Is this medical advice?

No. Please follow your doctor's advice and scans for your pregnancy care.

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