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Due Date Calculator

Calculate your estimated due date based on the first day of your last menstrual period using Naegele's rule.

๐Ÿ‡ฉ๐Ÿ‡ฐ All calculations are based on Danish rules, rates, and currency (DKK). This calculator is translated for convenience but applies exclusively to Denmark.

Due Date Calculator (Terminsdato)

The due date, or terminsdato in Danish, is the estimated date when your baby is expected to be born. It is calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle is longer or shorter than the standard 28 days, the calculation is adjusted accordingly.

How Naegele's Rule Works

Naegele's rule assumes ovulation occurs on day 14 of a 28-day cycle. For cycles that differ from 28 days, the estimated due date is adjusted by the difference. For example, if your cycle is 30 days, 2 extra days are added to the due date. While this is an approximation, it is the standard method used by healthcare professionals worldwide as a starting point for pregnancy dating.

Important Notes

Only about 5% of babies are born on their exact due date. Most births occur within two weeks before or after the estimated date. In Denmark, the first ultrasound scan (nakkefoldsskanning) at week 11โ€“14 provides a more accurate estimate. This calculator gives you a quick initial estimate โ€” always confirm with your midwife (jordemoder) or doctor.

Frequently Asked Questions

How is the due date calculated?

The due date is calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. If your cycle differs from 28 days, the calculation is adjusted by the difference.

How many babies are born on their exact due date?

Only about 5% of babies are born on their exact due date. Most births occur within two weeks before or after the estimated date. The due date is best understood as the middle of a window rather than an exact prediction.

Can ultrasound give a more accurate due date?

Yes, the first ultrasound scan (nuchal translucency scan) at weeks 11-14 provides a more accurate estimate by measuring the baby's size. In Denmark, this scan may adjust the due date calculated from the last menstrual period.

What does 'full term' mean?

A pregnancy is considered full term from week 37. Births between weeks 37-42 are considered normal. Before week 37 is premature, and after week 42, labour is typically induced due to increased risks.

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