Pregnancy Due Date Calculator

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Estimate your baby's due date from your last period or conception date, with gestational age, trimester and conception date. Free and instant.

days
The typical length of your cycle, used to adjust the estimate.
Estimated due date –
Gestational age today –
Trimester –
Estimated conception –
Uses Naegele's rule: due date = last period + 280 days, adjusted for cycle length. Conception is assumed about 14 days after the last period. An estimate only — confirm with your healthcare provider.

About Pregnancy Due Date Calculator

The pregnancy due date calculator estimates when your baby is likely to arrive, working from either the first day of your last period or a known conception date. Alongside the due date, it reports your gestational age today, your current trimester and the estimated conception date.

The math follows Naegele’s rule: due date = last period + 280 days (40 weeks), adjusted for your average cycle length when it differs from 28 days. In conception mode, the tool assumes conception occurs about 14 days after the last period and counts forward from your entered date instead.

It is a free way to get an instant estimate before an appointment, plan announcements or track which trimester you are in week by week.

How to use Pregnancy Due Date Calculator

  1. Choose what to calculate from: last period or conception date.
  2. Enter the corresponding date — the first day of your last period, or the conception day.
  3. In last-period mode, adjust your average cycle length so the estimate reflects your cycle.
  4. Read the estimated due date, gestational age today, trimester and estimated conception date.

Frequently asked questions

Only about 4–5% of babies arrive on their exact due date; most are born within two weeks either side. The calculation is a well-established estimate, and an early ultrasound usually refines it.

The classic obstetric formula this tool uses: add 280 days (40 weeks) to the first day of your last menstrual period. The calculator also shifts the result when your cycle length differs from 28 days.

Use conception mode — it counts 266 days forward from the actual conception day, skipping the assumption that ovulation happened mid-cycle. It is typically the more direct estimate for IVF or tracked cycles.

The calculator reports your current trimester from gestational age: the first trimester covers the beginning of pregnancy, the second the middle weeks, and the third the final stretch to 40 weeks.

Treat it as an estimate, not medical advice. Cycle variation and ovulation timing shift real dates, so confirm your due date with your healthcare provider, who can date the pregnancy precisely by ultrasound.
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