What this calculator is actually answering
The question is simple: how many months or years would it take for the current balance and monthly contribution to compound into the first 1,000,000 if the return assumption stayed constant? The answer is a timeline estimate, not a statement about what markets will actually deliver.
That makes this tool slightly different from a generic future-value calculator. The fixed milestone gives the result a concrete meaning, while the supporting schedule helps show how much of the path comes from deposits and how much comes from growth.