Work out months lived instantly with clear inputs, formula shown and shareable results.
Complete months are counted by month arithmetic rather than by dividing days, because months vary in length. Someone born 29 February 1988 has lived 462 complete months by 4 September 2026 - 38 years and 6 months. The day-of-month comparison is what prevents an incomplete final month from being counted.
Complete months
months = (year difference x 12) + month difference, less one if the day of month has not been reached
Years and remainder
years = floor(months / 12); remainder = months mod 12
Because that gives a fractional average rather than complete calendar months, and it drifts by several days over a lifetime.
The day-of-month comparison uses 29, so in non-leap years the month completes on 1 March under this arithmetic.