Age In Months Calculator

How to Calculate Your Age in Months

Months are the calendar unit behind birthdays, leases, and child development charts. The Age in Months Calculator reports how many complete months have passed since your birth date.

How the Calculation Works

The tool does not divide days by 30. It first finds the calendar breakdown of years and months, then converts everything to months:

$$M_{\text{total}} = 12 \times Y + M$$

Here Y is the number of complete years and M is the number of additional complete months. Any leftover days are reported separately and are never turned into an extra month.

Worked Example

Take June 15, 1990 as the birth date and September 14, 2020 as the reference date. The span is 30 complete years plus 2 extra months and 30 days, so the month total is:

$$M_{\text{total}} = 12 \times 30 + 2 = 362 \text{ months}$$

Dividing the same span by 30 days would suggest about 368 months, which overstates the true calendar age. That gap appears because months range from 28 to 31 days. For related views, see the Age in Years Calculator or the Age in Years, Months and Days Calculator.