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 (Baby-Friendly)

Pick a birth date and an optional target date. We’ll show weeks and months—clear and kid-friendly, all client-side.

Dates

Date of Birth

Target Date (optional, defaults to today)

Result: Enter dates and click Calculate.

How we count weeks & months

Weeks: Whole weeks + remaining days (e.g., 12 weeks, 3 days) and a decimal view (e.g., 12.43 weeks).

Months:

Calendar months — whole months + days (e.g., 3 months, 5 days).
Decimal months — total days ÷ average month length ≈ 30.44.

Leap years and real month lengths are respected. Feb 29 birthdays 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.

Age in Weeks & Months (Baby-Friendly)

Dates

How we count weeks & months

FAQs

Which month should I use?

Can I choose a future date?

Is my data private?

Explore more tools