Baby Age Calculator

Your baby’s exact age in months, weeks and days. Free, private and instant.

How to use the Baby Age Calculator

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

About the Baby Age Calculator

Enter your baby’s date of birth to see their exact age in years, months, weeks and days, the date of the next monthly birthday and a chart of when babies typically reach milestones such as smiling, rolling, sitting, crawling and walking.

Also known as: how old is my baby, baby age in months, baby age in weeks and days, age calculator for babies.

Worked example

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

Baby’s date of birth: 28 Jul 2026

Your baby is: 3 months old (3 months 8 days). Your baby is 3 months 8 days old (100 days, or 14 weeks). The next monthly birthday is 28 Nov 2026.

Age: 3 months 8 days
In days: 100
In weeks: 14 weeks 2 days
In months: 3.3

Formula and cut-offs

Age = today - date of birth, counted in whole calendar months plus remaining days. Weeks = days / 7. Milestone windows are typical ranges, not deadlines.

Frequently asked questions

How do I calculate my baby’s age in months?

Count whole calendar months since the birth date. A baby born on 10 January is 3 months old on 10 April.

When do babies start walking?

Most walk alone between 9 and 15 months.

Should I use corrected age for a premature baby?

Yes, for milestones until about 2 years. Use the Corrected Age calculator.

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 2026-10-25. This calculator is for education only and is not medical advice. See the medical disclaimer.