Due Date Calculator

An estimated due date, how far along you are, and what usually happens when.

Estimated due date —

Weeks pregnant today

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Days to go

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Full term (39w to 40w6d)

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Your pregnancy, week by week

Dashed box: 37 to 42 weeks, the usual window for birth

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Typical timing in US prenatal care (ACOG, CDC). Your midwife or doctor sets your own schedule.

How this is calculated

Pregnancy is counted from the first day of the last menstrual period, about two weeks before conception, so a full-length pregnancy is 280 days (40 weeks).

Last period due date = first day + 280 days (+ cycle length − 28) Conception due date = conception + 266 days IVF due date = transfer + 261 days (day-5 embryo) = transfer + 263 days (day-3 embryo) Ultrasound due date = scan date + (280 − age at scan in days)

Weeks are counted in completed weeks and days: "16 weeks 3 days" is written 16w3d. The trimesters are weeks 0 to 13w6d, 14w0d to 27w6d, and 28w0d to birth. Early term is 37w0d to 38w6d, full term 39w0d to 40w6d and late term 41w0d to 41w6d.

A due date is an estimate. Most babies are born between 37 and 42 weeks, and only a few arrive on the date itself. When an early ultrasound disagrees with the date from your last period by more than a set margin, clinicians usually go by the scan.