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Pregnancy Due Date Calculator

Estimate a due date from the last period, conception or IVF transfer date, with weeks pregnant and key dates.

Result

Enter your values and select Calculate to see the result.

Runs in your browser — nothing you enter is sent to a server.

How the Pregnancy Due Date Calculator works

Pregnancy is dated from the first day of the last menstrual period (LMP), about two weeks before conception. Naegele's rule adds 280 days (40 weeks) to the LMP, adjusted for cycles longer or shorter than 28 days. You can also start from the conception date or an IVF transfer date. The result shows how far along the pregnancy is today, the trimester and key dates.

Formulas

From the last period

due date = LMP + 280 days + (cycle length − 28 days)

Other starting points

conception + 266 days · 3-day IVF transfer + 263 days · 5-day transfer + 261 days

Examples

Last period on 1 June 2026

With a 28-day cycle the due date is 8 March 2027; on 30 September 2026 that's 17 weeks and 2 days.

A 32-day cycle

The same period date moves the due date 4 days later, to 12 March 2027.

Frequently asked questions

How accurate is the due date?

It's an estimate. Few babies arrive exactly on it; most are born within about two weeks either side. An early ultrasound usually gives the most accurate dating.

When do the trimesters change?

This calculator uses the common split: first trimester to 13 weeks, second to 27 weeks, third after that.

Is my information private?

Yes. The dates never leave your browser and nothing is stored.

Information:

Good to know

For general information only — not medical advice, diagnosis or treatment. Talk to a doctor or other qualified professional about your health.

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