Pregnancy calculator
Calculation of due date, date of birth and stage of development of the baby
to calculate your due date
* Calculation using Naegele's formula. Actual date may vary.
Pregnancy calculator
🤰 When to expect a baby: accurate calculation of maximum allowance
Pregnancy lasts on average 280 days (40 obstetric weeks). Our calculator will help you find out your estimated date of birth (ED), current due date and trimester, based on the first day of your last menstrual period.
How does the calculation work?
We use the proven obstetricNägelerule:
- The start date of the last menstruation is taken.
- 1 year is added.
- 3 months are deducted.
- Add 7 days.
If your cycle differs from the standard 28 days, the calculator will automatically adjust the calculation.
Useful tools for expectant mothers
To make it easier for you to plan and monitor your health, we recommend using our other services:
- Planning: If you are just preparing for conception, determine the best days using ovulation calculator.
- Health: Monitor your weight gain and general condition using BMI calculator (body mass index).
- Waiting: Want to know exactly how much time is left until the meeting? Set countdown timer.
Frequently asked questions (FAQ)
🔹 Why is the ultrasound term different from the calculator term?
This is normal. The calculator calculates the “obstetric period” (from menstruation), and the ultrasound shows the real age of the fetus (“embryonic period”), which is usually 2 weeks less. Doctors in the antenatal clinic focus specifically on the obstetric period.
🔹 What to do if the cycle is irregular?
With an irregular cycle, the Naegele method gives a large error. In this case, the most accurate method for determining PDR will be ultrasound of the first screening (at 11–13 weeks).
🔹 When to go on maternity leave?
Usually, sick leave for pregnancy and childbirth is issued at 30 weeks (for a singleton pregnancy) or at 28 weeks (for a multiple pregnancy). The calculator will show you the current week so you can plan your vacation.