Pregnancy Due Date Calculator

Estimate your pregnancy due date from your last period, and see how far along you are in weeks and which trimester.

Estimate your pregnancy due date from the first day of your last period, and see how many weeks pregnant you are and which trimester you are in. This due date calculator uses Naegele's rule, the standard 40-week count midwives and doctors start from.

Read the guide: How Your Pregnancy Due Date Is Calculated

How it works

  1. 1

    Enter your last period

    Add the first day of your last menstrual period.

  2. 2

    See your due date

    The estimate uses Naegele's rule: 280 days from that date.

  3. 3

    Track your progress

    View your current week, days and trimester.

Instant & 100% private — nothing is uploaded

Every calculation runs locally in your browser. The measurements, dates and details you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.

Frequently asked questions

How is the due date estimated?
It adds 280 days (40 weeks) to the first day of your last period, assuming a regular 28-day cycle. Only about 1 in 20 babies arrives exactly on the date.
How accurate is it?
It is a reasonable estimate, but your clinician's dating ultrasound, especially in the first trimester, is more accurate, particularly with irregular cycles.
Can I use it if my cycle is not 28 days?
The standard estimate assumes a 28-day cycle, so a longer or shorter cycle can shift the date by a few days. An early dating scan gives a more accurate due date if your cycle is irregular.

Important

These calculators give general, informational estimates and are not medical advice, diagnosis or treatment. Everyone is different — for decisions about your health, talk to a qualified clinician.

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