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Due Date Calculator

When is your baby due? Calculate your estimated due date, your current pregnancy week, the trimester and maternity-protection dates — using the Naegele rule, from your last period, conception or IVF transfer.

100% freeNo data storedBased on the Naegele rule

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The first day of your last period is the starting point of the Naegele rule.

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Guide: Due Date & Pregnancy

Worth knowing about the Naegele rule, pregnancy weeks and trimesters

Calculating Your Due Date: How the Naegele Rule WorksFeatured

Calculating Your Due Date: How the Naegele Rule Works

The Naegele rule determines the estimated due date from the first day of the last period. How the formula works, why cycle length matters and what the date really means.

2026-07-037 min read
Understanding Pregnancy Weeks (SSW)

Understanding Pregnancy Weeks (SSW)

Why are pregnancy weeks counted from the last period and not from conception? What does the notation "12+3" mean and how are the three trimesters divided? A clear overview.

2026-07-036 min read
The Three Trimesters: What Happens in Each Phase of Pregnancy

The Three Trimesters: What Happens in Each Phase of Pregnancy

From implantation to birth: what happens in each of the three trimesters, which milestones lie ahead and which check-ups matter — an overview of the 40 weeks.

2026-07-038 min read
Calculating Maternity Protection: Dates, Start and End

Calculating Maternity Protection: Dates, Start and End

Maternity protection begins six weeks before the due date and ends eight (or twelve) weeks after birth. How the periods are calculated under § 3 MuSchG and what applies if the baby arrives earlier or later.

2026-07-038 min read
Overdue: What Happens When You Pass Your Due Date

Overdue: What Happens When You Pass Your Due Date

The due date has passed and your baby is taking its time? Why this is usually no cause for concern, when a pregnancy is considered post-term and how medical monitoring works.

2026-07-037 min read

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Frequently Asked Questions

Using the Naegele rule, the calculator adds 280 days (40 weeks) to the first day of your last period. If your cycle length differs from 28 days, the date is corrected accordingly. If you know the day of conception, 266 days are added; with IVF the date is derived exactly from the transfer date.

Only about 4% of babies are born exactly on the due date. Most arrive in the two weeks before or after. The due date is therefore a point of reference, not a fixed date. The ultrasound dating done by your doctor is the decisive figure.

The exact moment of conception usually cannot be determined, whereas the first day of the last period is easy to remember. That is why the medical pregnancy week (SSW) is counted from that day. As a result, you are already in the 3rd week at conception — by this count a pregnancy lasts 40 weeks.

The "week + day" notation states the completed pregnancy weeks and the additional days. "12+3" therefore means 12 full weeks and 3 days — you are then in the 13th week. The calculator shows you this figure automatically for today.

Under § 3 of the German Maternity Protection Act, the protection period starts six weeks before the due date and ends eight weeks after birth. For premature and multiple births, the period after birth is extended to twelve weeks. The calculator shows the expected dates based on the due date.

No. The entire calculation runs directly in your browser. Your sensitive health data as defined by Art. 9 GDPR is never sent to a server, stored or analysed. Only if you share your result via a link are the values contained in that address — nowhere else.