Health & fitness

Pregnancy due date

Estimate the due date and week of pregnancy from the last period.

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How it works

Naegele's rule: last period + 280 days (adjusted for cycle length). Only an ultrasound gives a precise date; your doctor or midwife is the reference.

Results are for guidance only and do not replace professional advice.

Worked example

With the default values:

  • First day of last period22 August 2026
  • Cycle length (days)28

you get:

  • Estimated due dateSaturday, 29 May 2027
  • Todayweek 10 + 0 days (1st trimester)
  • Days left210

Frequently asked questions

How does the “Pregnancy due date” tool work?

Naegele's rule: last period + 280 days (adjusted for cycle length). Only an ultrasound gives a precise date; your doctor or midwife is the reference.

What do I need to enter?

Just fill in: first day of last period, cycle length. The result updates as you type.

Can you give an example?

First day of last period: 22 August 2026; Cycle length (days): 28 → Estimated due date: Saturday, 29 May 2027; Today: week 10 + 0 days (1st trimester).

Is this calculator free, and is my data private?

Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.