Pregnancy Due Date Calculator

Estimate your due date from the first day of your last period.

First day of last period (LMP)

Average cycle length (days)

Estimated due date

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Conception (approx.)

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Current gestation

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Trimester

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Days remaining

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Naegele\'s rule = LMP + 280 days (40 weeks), assuming a 28-day cycle with ovulation on day 14. For other cycle lengths we adjust ovulation accordingly. Only ~4–5% of babies arrive on their estimated due date; ±2 weeks is normal.

How this is calculated

Naegele's rule adds 280 days (40 weeks) to the first day of your last menstrual period — the standard obstetric method. We adjust for cycle length: if your cycle is longer than 28 days, ovulation happens later, so the due date moves out by the same number of days.