Current for 2026•As of: July 2026

Baby Week Calculator calculate age in weeks.

Enter the birth date – instantly see age in weeks, days and months plus upcoming checkups

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Baby Week Calculator

Exact baby age in weeks, days and months – plus guidance on the U checkups.

Please enter the date of birth and reference date

Note: The U-checkup display is for appointment orientation only, based on the Children's Guideline (Kinder-Richtlinie) of the Federal Joint Committee (G-BA). It is not a developmental diagnosis and does not replace a medical examination or consultation.

Important note

These calculations are for non-binding information only and do not replace professional tax advice. All information without guarantee. Learn more

Sources & calculation basis

Our calculations are based on the following official sources (as of: July 2026):

How the baby week calculator determines age

Exact date difference in weeks, days and months

The baby week calculator calculates your baby's exact age between the date of birth and a freely selectable reference date – by default today's date. The main result is the full weeks of life plus remaining days, since babies develop especially quickly in their first year of life and stating the age in weeks is significantly more precise than a plain month figure.

In addition, the calculator shows the age calendrically in years, months and days as well as the total days since birth. As a point of orientation, it also shows which time window of the legally mandated U checkups (U1–U9) your baby currently falls into, or which appointment is coming up next.

U checkups U1 to U9 at a glance

Time windows under the Children's Guideline (Kinder-Richtlinie) of the Federal Joint Committee (G-BA)

Legally mandated preventive checkups

U1 · Immediately after birth
Initial examination right after birth: breathing, heartbeat, reflexes and visibly detectable malformations.
U2 · Day 3–10 of life
Comprehensive physical examination, metabolic screening and newborn hearing screening.
U3 · Week 4–5 of life
Hip ultrasound, reflex testing and an initial assessment of vision and hearing.
U4 · Month 3–4 of life
Check of motor development, response to stimuli and vaccination counseling.
U5 · Month 6–7 of life
Assessment of gross and fine motor skills, growth and nutrition.
U6 · Month 10–12 of life
Check of motor skills (sitting, crawling), early language development and social behavior.
U7 · Month 21–24 of life
Assessment of language development, walking and early toilet training.
U7a · Month 34–36 of life
Additional examination of vision and hearing, speech, behavior and obesity prevention.
U8 · Month 46–48 of life
Check of gross/fine motor skills, speech and social behavior before starting school.
U9 · Month 60–64 of life
Final preventive examination before starting school: vision, hearing, speech and motor skills.

Important: This overview is for appointment orientation only. It is not a developmental diagnosis and does not replace a medical examination. Each checkup also has a tolerance window within which the appointment can still be attended without disadvantage. Source: Federal Joint Committee (Gemeinsamer Bundesausschuss), Children's Guideline (Kinder-Richtlinie) (last amended 21 March 2024, in effect since 13 July 2024).

Calculation example

Date of birth 01/01/2026, reference date 03/01/2026

Date of birth 01/01/2026, reference date 03/01/2026
ItemAmount
Date of birth01/01/2026
Reference date03/01/2026
Total days59
Full weeks8 weeks
Remaining days3 days

Frequently asked questions about the baby week calculator

Age in weeks, U checkups and tolerance windows explained

The calculator computes the difference between the date of birth and the reference date (default: today) in total days and divides it by 7 to get full weeks of life. It also outputs the age calendrically in years, months and days – the same borrow logic as the age calculator, exact to the day.

In the first year of life a baby changes very quickly, so stating the age in weeks is more precise than "X months old". Many checkup and vaccination appointments (e.g. U2 in week 2 of life, U3 in weeks 4–5 of life) are also specified in weeks or days of life rather than in months.

From U1 (immediately after birth) to U9 (month 60–64 of life), the Children's Guideline (Kinder-Richtlinie) of the Federal Joint Committee (G-BA) provides for ten early-detection checkups within the first six years of life. Each checkup has a fixed time window as well as a tolerance window within which the appointment can be caught up on without disadvantage.

No. The display only shows which official time window your baby currently falls into, or which appointment is coming up next. It does not replace a medical examination, consultation or diagnostics. Please arrange the appointments through your pediatric practice.

Within the tolerance window (e.g. U6: month 9–14 of life instead of just 10–12), the checkup can usually still be covered as usual by the statutory health insurer. Outside the tolerance window, you should consult your pediatric practice as soon as possible.

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