Determining the exact age of the apostle Matthew at the time of his encounter with Jesus Christ is impossible based on available biblical and historical sources. The Gospels do not provide specific dates or ages for any of the apostles. Therefore, any assertion regarding his age when called to discipleship would be speculative.
Understanding the likely societal norms of the time can offer some contextualization. Men in that era typically entered adulthood and participated in trades or professions at a younger age than is common today. It is reasonable to infer that Matthew was likely an adult, capable of performing his tax collecting duties, and therefore probably at least in his late teens or early twenties. The significance of this inquiry lies in the desire to understand the dedication and commitment of individuals who chose to follow Jesus, leaving behind established lives and occupations.