🤰 Pregnancy Due Date Calculator

About this Pregnancy Due Date Calculator

A full-term pregnancy lasts about 280 days, or 40 weeks, counted from the first day of the last menstrual period. This is known as Naegele's rule and is the same method most clinics use for a first estimate. An ultrasound scan later in pregnancy can refine the date if your cycle is irregular.

How to use it

1. Enter the first day of your last menstrual period.
2. Press Calculate Due Date.
3. See the estimated due date, 280 days later.
4. Check your current week and trimester estimate for today.

Example

If the last period started on 1 Jan 2026, adding 280 days gives an estimated due date of 8 Oct 2026.

Frequently asked questions

What if my cycle is not 28 days?

The 280-day rule assumes a 28-day cycle. Your doctor may adjust the date using an early ultrasound scan.

Is the due date exact?

No. It is an estimate; only about 1 in 20 babies are born on the exact due date.

How are pregnancy weeks counted?

Weeks are counted from the first day of the last period, so you are about two weeks pregnant at conception.

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