Due Date Calculator

Enter the first day of your last period or known conception date.

First day of last menstrual period (YYYY-MM-DD)

Average cycle length (days)

Estimated due date —

Current weeks pregnant —

First trimester ends —

Second trimester ends —

Estimated conception date —

Naegele's rule: EDD = LMP + 280 days (adjusted for cycle length). Only 5% of babies arrive on their due date. The normal range is 37–42 weeks.

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How Due Dates Are Calculated

The estimated due date (EDD) is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). For cycles longer or shorter than 28 days, the date is adjusted.

Due dates are estimates. Only about 5% of babies are born on their exact due date. Most arrive within two weeks before or after. Your healthcare provider may adjust the date based on ultrasound measurements.

Estimated due date (EDD) is calculated by Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). Alternatively: add 1 year, subtract 3 months, add 7 days. A LMP of January 1 gives an EDD of October 8. This assumes a 28-day cycle with ovulation on day 14.

Cycle length adjustment: Naegele's rule assumes a 28-day cycle. For cycles shorter than 28 days, the EDD is earlier; for longer cycles, the EDD is later. The adjustment = (actual cycle length − 28 days). A 35-day cycle shifts EDD 7 days later than the standard Naegele calculation.

Only about 4–5% of babies are born on their calculated due date. Normal delivery is between 38–42 weeks. "Full term" by ACOG definition is 39 0/7 to 40 6/7 weeks; "early term" is 37–38 weeks. Due date estimates should be verified and refined by ultrasound, which is most accurate before 14 weeks gestation.

IVF due date: for IVF, due date is calculated from egg retrieval date (add 266 days for day-0 transfer, 264 days for day-3 transfer, 261 days for day-5 blastocyst transfer). The IVF calculation is independent of LMP and is typically more precise.

This calculator is for informational purposes only. All pregnancy dates should be confirmed with your healthcare provider and ultrasound measurements.