Infant Age in Weeks Calculator

Baby’s age in weeks and days, with week-by-week events. Free, private and instant.

How to use the Infant Age in Weeks

  1. Pick baby’s date of birth.
  2. Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.

About the Infant Age in Weeks

Many newborn milestones and checkups are given in weeks. Enter the birth date to see your baby’s age in weeks and days, the dates they reach 6, 10 and 14 weeks and 6 months, and a timeline of common newborn events such as growth spurts, vaccines and sleep changes.

Also known as: baby weeks old calculator, how many weeks old is my baby, infant age calculator, newborn age in weeks.

Worked example

Dates in this example are worked out as if today were 5 Nov 2026.

Your baby is: 8 weeks + 4 days (Early infancy (4-12 weeks)). Your baby is 8 weeks and 4 days old (60 days in total). Next week starts on 8 Nov 2026.

Formula and cut-offs

Weeks = (today - date of birth) / 7, shown as whole weeks plus days. Common routine immunisation ages in many programmes: 6, 10 and 14 weeks.

Frequently asked questions

How many weeks is my baby?

Divide the number of days since birth by 7. This calculator does it for you.

When are the 6 week vaccines due?

At 6 weeks of age, which is 42 days after birth. Check your own schedule for exact timing.

What happens at 6 to 8 weeks?

Many babies smile socially, and fussiness often peaks. The 6-week check is common.

Sources and references

Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.

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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.