Jeremiah was approximately 13 to 17 years old when God called him to be a prophet. Some sources suggest he was about 13 to 16 years old based on the timing of King Josiah's reign when Jeremiah began his ministry, while others indicate he was around 17 years old when he received his calling from God. Jeremiah himself referred to himself as "a boy" or "a child" when God called him, indicating his youth at that time. More specific references point to the call occurring around the 13th year of King Josiah's reign, which correlates with Jeremiah being in his early to mid-teens.