Due Date Calculator

A due date is an estimate: only about 1 in 20 babies arrives on it, and most come within two weeks either side. It is still the date everything else is planned around, from scans to leave.

How it works

From your last period: add 280 days (40 weeks), adjusted if your cycle is longer or shorter than 28 days. From conception: add 266 days. From an IVF transfer: add 261 days for a day-5 embryo or 263 for a day-3 embryo. Your dating scan may move the date; if it does, use the scan's.

Questions parents ask

Why does my due date count from my period, before I was pregnant?

Because the first day of the last period is a date most people know, while ovulation usually is not. The convention adds two weeks before conception, which is why pregnancy is "40 weeks" although the baby grows for about 38.

How accurate is it?

From the last period, about half of babies arrive within 3 to 4 days of the estimate and 9 in 10 within two weeks. An early scan (before 14 weeks) is the most accurate dating method.

When does Bheeli come in?

From the day your baby arrives: feeds, sleep, growth, milestones and a companion to ask anything, at any hour.

Sources

• ACOG Committee Opinion 700: Methods for estimating the due date (2017)
• NHS: Your pregnancy week by week

Bheeli offers general guidance, not medical advice.