Support: Due Date Calculator

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Common questions

How is a due date calculated?

By convention it is 280 days (40 weeks) after the first day of your last menstrual period, as described in ACOG Committee Opinion 700. That assumes a 28-day cycle; the calculator moves the date by the difference for a longer or shorter cycle.

How do I calculate my due date from conception?

Add 266 days (38 weeks) to the date of conception. Choose Conception and type the date.

How is an IVF due date calculated?

From the transfer date and the embryo's age: 261 days after the transfer of a day-5 embryo and 263 days after a day-3 embryo, per ACOG Committee Opinion 700. Choose IVF transfer and pick the embryo's age.

How many weeks pregnant am I?

Count the days since the first day of your last period and divide by 7; the remainder is the extra days. The calculator shows it for today as weeks and days.

What do early term, full term and late term mean?

According to ACOG Committee Opinion 579, early term is 37 weeks 0 days to 38 weeks 6 days, full term 39 weeks 0 days to 40 weeks 6 days, late term 41 weeks 0 days to 41 weeks 6 days, and postterm from 42 weeks.

Why did my doctor give me a different due date?

An ultrasound in the first trimester dates a pregnancy more accurately than the last period, so the date may be changed after an early scan. Choose Ultrasound and type the age from the report to match it. Always use the date your doctor or midwife gives you.

When does each trimester start?

The first trimester runs to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth.

Is anything sent anywhere?

No. The dates you type are worked out in your browser and are not sent to us or stored.