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Pregnancy Due Date Calculator

When is your estimated due date (EDD)? Enter how many days ago your last period started and instantly get your current week of pregnancy, trimester, and how many days remain until your due date.

✓ Vérifié par Julian Bronski · mis à jour juin 2026

Vos informations

days
0280+
days
2135+

Résultat

Week of pregnancy (gestational)
Days remaining until due date
Trimester
Estimated conception (days ago)
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Comment fonctionne le Pregnancy Due Date Calculator

The calculation uses Naegele's Rule, the medical standard since 1812: the estimated due date (EDD) is 280 days (40 weeks) after the first day of your last menstrual period (LMP). If your cycle length differs from 28 days, the difference is added or subtracted.

Formula: EDD = LMP + 280 + (cycle length − 28) days. Gestational age is counted from day 1 of your last period: week = ⌊days since LMP ÷ 7⌋ + 1. Trimesters: weeks 1–13 = first trimester, weeks 14–27 = second trimester, week 28+ = third trimester.

Questions fréquentes

How accurate is the estimated due date?
Only about 5% of babies are born on their exact due date. A window of ± 2 weeks (weeks 38–42) is considered a normal birth range. An ultrasound between weeks 11–14 (dating scan) provides the most accurate individual estimate.
When does each trimester start?
The first trimester covers weeks 1–13 (organ formation, higher miscarriage risk). The second trimester (weeks 14–27) is generally the most comfortable phase. The third trimester begins at week 28 and ends with delivery around week 40.
What is gestational age vs. fetal age?
Gestational age (used by doctors and shown here) counts from the first day of your last period – about 2 weeks before conception. Fetal age (conceptional age) counts from actual fertilisation. If gestational age is 10 weeks, fetal age is approximately 8 weeks.
Ne constitue pas un conseil financier ou médical. Sans garantie.

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