What is the difference between calendar months and decimal months?

Calendar months count whole months and remaining days between the dates (e.g., 3 months 5 days). Decimal months divide total days by the average month length (≈30.44 days), giving a single number (e.g., 3.17 months).

Does it handle leap years and different month lengths?

Yes. Month and day differences respect real calendar lengths and leap years.

Yes. All calculations run locally in your browser; nothing is uploaded or stored.

Age in Weeks & Months Calculator – Baby Age by Weeks & Months

Age in Weeks & Months (Baby-Friendly)

Pick a birth date and (optionally) a target date. We’ll show age in weeks and months—clear and kid-friendly.

Date of Birth

Target Date (optional, defaults to today)

Result: Enter dates and click Calculate.

How We Count Weeks & Months

Weeks: We show whole weeks and remaining days (e.g., 12 weeks, 3 days) and also a decimal weeks view (e.g., 12.43 weeks).

Months: Two views help different needs:

Calendar months count whole months plus days between the dates (e.g., 3 months, 5 days).
Decimal months use the average month length ≈ 30.44 days (Gregorian), giving a single number (e.g., 3.17 months).

This tool accounts for leap years and real month lengths. For 29 Feb birthdays, we follow calendar arithmetic naturally.

FAQs

Which month should I use?

For baby milestones, many parents prefer calendar months. Decimal months are handy for charts or spreadsheets.

Can I choose a future date?

Yes—set any Target Date to see age at that time (e.g., first day of school).

Is my data private?

Yes. Everything runs in your browser; no dates are uploaded.

⭐ Starlight Tools / Age in Weeks & Months