Pregnancy Due Date Calculator

About the pregnancy due date calculator

A normal pregnancy lasts about 40 weeks (280 days), counted from the first day of your last period. This calculator gives you your estimated due date, how many weeks and days pregnant you are today, your trimester, and the days to go.

Choose what you know:

• The first day of my last period — the most common way. If your cycle is not 28 days, type your cycle length and the date moves with it.
• The date of conception — the due date is 266 days later.
• My IVF transfer date — choose a day 3 or a day 5 embryo.
• An ultrasound date and age — type the weeks and days the scan gave you.

A table below the result shows the main dates: the end of the first trimester, the detailed ultrasound, the end of the second trimester, full term, and your due date.

How to use it

• Choose I know — last period, conception, IVF transfer or ultrasound
• Pick the date. For a last period, also type the cycle length (28 is the average)
• Read your due date, the weeks and days, your trimester and the days to go
• Check the milestone table for the dates of the key weeks

Due dates from the last period

For a cycle of 28 days, this is the due date for a last period that began on the 1st of the month:

Milestones for a last period on 1 January

Naegele's rule — the quick way

Take the first day of your last period, add 7 days, subtract 3 months, and add a year. It gives the same answer as counting 280 days for a 28-day cycle. The calculator also adjusts for a longer or shorter cycle, because ovulation moves with it.

Trimesters

• 1st trimester: weeks 1 to 12 — the baby's organs form
• 2nd trimester: weeks 13 to 27 — usually the most comfortable weeks
• 3rd trimester: weeks 28 to birth — the baby grows and gains weight

How exact is a due date?

Only about 5 in 100 babies are born on the due date. A healthy birth is anything from 37 to 42 weeks. Treat the date as the middle of a window, not as a deadline. Your doctor or midwife may change it after an early ultrasound.

Frequently asked questions

How do I calculate my due date?

Count 280 days from the first day of your last period. The calculator does it for you and adjusts for your cycle length.

How many weeks pregnant am I?

Weeks are counted from the first day of your last period — about two weeks before conception. The result shows weeks and days pregnant today.

What if I do not know my last period?

Choose An ultrasound date and age, or ask your doctor. An early ultrasound is the most exact way to date a pregnancy.

Is the due date the same for IVF?

The IVF due date uses the transfer date and the age of the embryo (day 3 or day 5) and is usually very exact.

Can the due date change?

Yes. If the first ultrasound shows a different age, your doctor may move it.

Is this medical advice?

No. It is a general guide. Always follow the advice of your doctor or midwife.

Good to know

• Your date is saved only in this browser
• Nothing you type is sent anywhere
• The dates use your language and your local date format

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