Calculate how long it takes to reach any savings target — or how much you need to save each month to hit your goal by a specific date. Accounts for interest compounding on your existing balance.
A savings goal has two variables you can control: how much you put in each month, and how long you give it to grow. The interest rate on your account is a third factor — but one you have less control over. The most powerful lever is time. Starting 12 months earlier on a 5-year goal is worth more than increasing your monthly contribution by $100, because every earlier dollar earns interest for the entire remaining period.
Your existing savings are not idle. Every dollar already saved is compounding right now — earning interest on interest every month before you add a single new contribution. A $5,000 existing balance at 5% annual return earns $250 in year one, $263 in year two, $276 in year three. That growth compounds automatically. The more you already have, the less new money you need to contribute to reach your goal on time.
The right return rate depends entirely on where the money lives. High-yield savings accounts currently pay 4 to 5% — appropriate for goals under 3 years where the money must stay safe. Index fund accounts average 7% over long periods in real terms — appropriate for goals 5 years or more away where short-term volatility is acceptable. Never use a high return rate for a short-term goal. If you need the money in 18 months, it should not be in equities.
For the "How long?" mode, the calculator iterates month by month — applying your monthly return rate to the current balance, then adding your contribution — and counts the months until the balance first reaches your goal. For the "How much/mo?" mode, it solves the future value of an ordinary annuity formula directly for the monthly payment. Both modes account for interest compounding on your existing savings from day one.
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