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Women's Health tool

Pregnancy Due Date Calculator

Estimate your due date from your last period, conception or IVF transfer date, with your pregnancy week, trimester and key milestones. Free, nothing stored.

Nothing you enter leaves your device.

Inputs

A due date from an ultrasound scan takes precedence. Few babies arrive on their due date.

Results

Enter values to see your results.

Simple steps

How it works

  1. 01

    Choose how to calculate: last period, conception date or IVF transfer.

  2. 02

    Enter the date, and your cycle length if you use your last period.

  3. 03

    Select Calculate to see your due date, how far along you are and the main milestones.

Good to know

Frequently asked questions

How is the due date calculated?

From the first day of your last period, 280 days (40 weeks) are added, adjusted if your cycle is longer or shorter than 28 days. From conception, 266 days are added; from an IVF transfer, 263 days for a day-3 embryo or 261 days for a day-5 embryo.

How many babies are born on their due date?

Only about 1 in 25. Most babies arrive between 37 and 42 weeks.

Which date should I trust, this or my scan?

A date from an early ultrasound scan is more accurate and takes precedence. Your midwife or doctor will use it.

How are pregnancy weeks counted?

From the first day of your last period, so you are counted as about two weeks pregnant at conception.

What are the trimesters?

The first trimester runs to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 to birth.

What do the milestones mean?

They show the end of the first trimester, the usual 20-week anomaly scan, full term at 37 weeks, the due date at 40 weeks and 42 weeks.

Is anything I enter stored or sent?

No. The calculation runs in your browser. Nothing you type is saved or sent to a server.

How it is calculated

Due date = first day of last period + 280 days + (cycle length − 28 days), or conception date + 266 days, or IVF transfer + 263 days (day-3 embryo) or + 261 days (day-5 embryo), following ACOG Committee Opinion 700. The pregnancy week is counted back from the due date (40 weeks).

Sources

Last reviewed: October 14, 2026

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