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Due Date Calculator

Estimated due date by Naegele’s rule, how many weeks pregnant you are, and your trimester — the way US clinicians date a pregnancy (ACOG).

Bitte gib den ersten Tag deiner letzten Periode ein.

Key facts

  • Due date by Naegele’s rule: first day of your last period + 280 days (40 weeks), adjusted for how your cycle length differs from 28 days.
  • “12 weeks 3 days” means 12 completed weeks plus 3 days — i.e. you are in your 13th week. Counting starts from the first day of your last period, not from conception.
  • The date is only an estimate: most babies arrive within two weeks either side of it, only a few on the exact day. ACOG bases dating on the last period AND an early ultrasound. Not medical advice.

FAQ

How is the due date calculated?
By Naegele’s rule: first day of your last period + 280 days (40 weeks), adjusted for how your cycle length differs from 28 days.
What does “how many weeks pregnant” mean?
It counts completed weeks + days from the first day of your last period. “12 weeks 3 days” = 12 completed weeks plus 3 days, i.e. your 13th week.
How accurate is the estimated due date?
It is an estimate. ACOG considers first-trimester ultrasound the most accurate dating method; when it differs meaningfully from the last period, the date is usually revised. Only a few babies arrive on the exact day.

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