Pregnancy Calculator for Due Date and Gestational Age
Estimate an expected due date and pregnancy timeline from the first day of the last menstrual period, conception date, a known due date, IVF transfer or ultrasound dating. The calculation exposes every day adjustment and lets you choose the as-of date used for gestational age.
Pregnancy dating inputs
Estimated pregnancy schedule
Pregnancy due-date and gestational-age guide
This pregnancy calculator provides a dedicated calculation workflow rather than a generic converter. Pregnancy dates are estimates. Clinical dating may prioritize an early ultrasound or other medical information when it differs from calendar-based calculation.
Dating from the last menstrual period
The standard LMP estimate adds 280 days to the first day of the last menstrual period. The calculator also adjusts by cycle length relative to a 28-day cycle.
Dating from conception or IVF
Conception dating adds 266 days. For IVF, embryo age is already known, so a day-3 transfer adds 263 days and a day-5 transfer adds 261 days to the transfer date.
Dating from ultrasound
Enter the date of the scan and the gestational weeks and days assigned at that scan. The calculator adds the remaining days required to reach 40 weeks.
Gestational age on a chosen date
Gestational age is measured from the calculated gestational start, about two weeks before conception in standard dating. The result reports completed weeks and remaining days.
Milestones are planning dates
The timeline includes common week markers such as 12, 20, 28, 37 and 40 weeks. Appointments, screening windows and clinical decisions must follow the treating professional’s plan.
Is the due date the predicted birth date?
No. It is an estimated 40-week reference date, and birth can occur before or after it.
Why does LMP dating begin before conception?
Gestational age conventionally starts from the last menstrual period, usually about two weeks before ovulation and conception.
Can this replace ultrasound dating?
No. A clinician may revise dates using ultrasound and the full clinical history.