With this free calculator, you can determine your estimated due date and your current week of pregnancy in just a few seconds. You can either use the first day of your last period as a starting point or, if you know it, your ovulation date. The latter is more accurate.
Standard: 268 Tage ab Eisprung – empirischer Median (Jukic et al. 2013). 266 Tage = klassische Naegele-Regel (wie im Mutterpass). Warum?
Errechneter Geburtstermin (ET)
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Aktuelle Woche
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Trimester
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Noch
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Der ET ist ein statistischer Schätzwert. Die natürliche Schwangerschaftsdauer schwankt erheblich; nur wenige Babys kommen exakt am ET zur Welt. Maßgeblich ist die Datierung durch deine Ärztin oder deinen Arzt per Ultraschall.
The estimated due date is approximately 280 days (40 weeks) counting from the first day of your last period—that’s the Naegele rule. However, it assumes that women have a standard 28-day cycle and ovulate on the 14th day. Do you know your actual ovulation, the date is Ovulation + 268 days More accurately, because your actual cycle is the basis, not some outdated model.
The classic calculation follows the Naegele rule: Add one year to the first day of your last period, subtract three months, and add seven days—this equals 280 days or 40 weeks. This rule of thumb assumes a regular 28-day cycle with ovulation around day 14. If your cycle is longer or shorter, ovulation shifts—and so does your due date. Our calculator takes this into account by allowing you to set your individual cycle length.
The actual starting point of a pregnancy is not the period, but ovulation. If you know when you ovulated, you can calculate the due date directly as the day of ovulation plus 268 days—without having to estimate your cycle length. This is precisely where the advantage of keeping a complete record of your cycle lies: OvulaRing It measures your core body temperature around the clock, shows you the day of your ovulation, and also your estimated due date. If you’re still planning to start a family, our Online Ovulation Calculator.
Gestational weeks (GW) are counted from the first day of your last period and expressed in full weeks plus days. “GW 12+3” therefore means 12 full weeks and 3 days. Because the count starts with your period, you’re technically already about two weeks “pregnant” before conception has even taken place. On your estimated due date, you’ll reach 40+0 weeks of pregnancy.
| Trimester | Time period | What happens |
|---|---|---|
| 1. Trimester | through week 12 of pregnancy | Organ development; early signs often include fatigue and nausea |
| 2. Trimester | Weeks 13 through 27 | Symptoms usually subside, and the first signs of movement become noticeable |
| 3. Trimester | a SSW 28 | The baby is growing rapidly; preparing for the birth |
The estimated due date (EDD) is 280 days or 40 weeks after the first day of your last period (Naegele’s rule). If your cycle length differs from 28 days, the due date will shift accordingly. If you know when you ovulate, the calculator provides a more accurate estimate: ED = ovulation plus 268 days.
SSW stands for “pregnancy week” and is counted starting from the first day of your last period. SSW 12+3 means that you are 12 full weeks and 3 days pregnant, so you are in your 13th week. On your estimated due date, you will reach 40+0 weeks of pregnancy.
The due date is a statistical estimate. Only a small percentage of children are born on that exact day; most births occur within a window of about two weeks before or after that date. The date determined by your doctor via ultrasound remains the definitive one.
Yes. If you know the date of your ovulation, select the “Ovulation” option in the calculator. The due date will then be calculated as the day of ovulation plus 268 days. This method is independent of cycle length and is therefore more accurate, especially for long or irregular cycles.
The first trimester lasts until the 12th week of pregnancy, the second from the 13th to the 27th week, and the third from the 28th week until birth. The boundaries may vary slightly depending on the definition.
The standard calculation based on your last period assumes that ovulation occurs on the 14th day of your cycle. If you ovulate earlier or later, the estimated date will be incorrect. If you know your actual ovulation date—for example, from a complete record of your cycle—this error is eliminated.
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