Due Date Calculator

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Estimate your due date and how far along you are today, from your last period, conception date or embryo transfer.

Calculated in your browser. Your data is never sent to a server.

Result

Enter the date to estimate the due date.

Pregnancy is dated medically from the first day of the last menstrual period and usually lasts 40 weeks (280 days), so you're about two weeks pregnant at conception.

If your cycle is longer or shorter than 28 days, enter its length to adjust the date. For IVF, choose the transfer date and embryo age.

How it's estimated

From last period: due date = first day of LMP + 280 days + (cycle length − 28).
From conception: due date = conception + 266 days.
Day-3 embryo transfer: + 263 days. Day-5: + 261 days.
Pregnancy today = days since the calculated start, in weeks and days. First trimester runs to the end of week 13, the second to the end of week 27.

Naegele's rule

Due date = LMP + 280 days
Cycle adjustment = cycle length − 28 days

This is an estimate only. First-trimester ultrasound dating is more accurate and your doctor is the reference. The tool gives no medical diagnosis.

Worked examples

Last period on 1 January 2026

With a 28-day cycle the due date is 8 October 2026. On 5 March 2026 you'd be exactly 9 weeks, in the first trimester.

A 35-day cycle

With an LMP of 1 January 2026, the date moves 7 days later to 15 October 2026.

Frequently asked questions

Will my baby arrive on the due date?

Only about 4% of births happen on the exact date; most fall within two weeks either side.

Why date from the last period, not conception?

The last period is usually known while the day of conception is hard to pin down. It's the standard medical convention.

Is my data stored?

No. Everything is calculated in your browser and no date is sent to our servers.

Content last reviewed: November 1, 2026