Pregnancy Week Calculator
Find your pregnancy week from your last period or due date, with trimester, days remaining, the baby's development stage and estimated size and weight.
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
How are pregnancy weeks counted?
Pregnancy weeks (SSW) are counted from the first day of the last menstrual period, not from conception. So at SSW 1-2, you are not actually pregnant yet. Conception typically occurs around SSW 3.
What happens in each trimester?
First trimester (up to 12+6): organ development. Second trimester (13+0 to 27+6): growth and movement. Third trimester (from 28+0): maturation and preparation for birth.
Does this calculator replace a doctor visit?
No. This calculator provides general orientation only. For medical questions, or before starting a diet, therapy or treatment, always consult a qualified physician or therapist.
Guide
What is the Pregnancy Week Calculator?
The pregnancy week calculator computes the current week of pregnancy and shows progress with development information.
How does the Pregnancy Week Calculator work?
Enter the first day of the last period. The calculator computes the current pregnancy week, day and remaining days until the due date. Information about the baby's development in each week is provided.
Key Data and Facts
Pregnancy: 40 weeks / 280 days. 1st trimester: up to 12+6. 2nd trimester: 13+0 to 27+6. 3rd trimester: from 28+0. Premature birth: before week 37.
Step-by-Step Guide
How to calculate your current week of pregnancy step by step: 1. Enter the first day of your last period: the pregnancy is counted from this day, even though fertilization takes place only about 2 weeks later. 2. Read off the current week of pregnancy: the calculator computes the completed weeks and days since the first day of the last period. Notation: SSW 12+3 = 12 completed weeks and 3 days = you are in the 13th week of pregnancy. 3. Assign the trimester: 1st trimester (up to 12+6): organ formation, nausea is common. 2nd trimester (13+0 to 27+6): baby movements become noticeable, a more stable phase. 3rd trimester (from 28+0): growth, preparation for birth. 4. Display the estimated due date: the due date is calculated automatically (280 days after the last period). 5. Read off the remaining days: the calculator shows how many days remain until the due date. 6. Plan maternity protection: maternity protection (Mutterschutz) begins 6 weeks before the due date and ends 8 weeks after the birth.
Calculation Example
Last period: 1 January 2026, today's date: 15 April 2026. Days elapsed: 104. Week of pregnancy: 104 / 7 = 14+6 (you are in the 15th week). Remaining: 176 days until the due date (8 October).
Sources
Official sources
Calculations are based on applicable German laws and official data:
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
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