How the timeline is calculated

There is no neat closed form once contributions and growth are both present, so the balance is stepped forward one month at a time:

balance = balance × (1 + r/12) + contribution

repeated until it reaches the goal. Growth is applied before the contribution, so a deposit made this month earns nothing this month, which is the conservative reading.

Worked example. $500 a month into a 0% account reaches $10,000 in exactly 20 months. At 6% it still lands in month 20, but overshoots to $10,489. The growth is real but, over a short horizon, small next to the deposits.

Educational content only, not financial advice. Results are estimates for learning purposes. Consult a qualified professional before making financial decisions.