Work backwards from a savings target: enter the amount you need, the date you need it by and the rate you expect, and get the exact monthly deposit that gets you there. Runs entirely in your browser — your numbers never leave this device.
This assumes a steady 6% return and a deposit every month. The interest shown is the part of your goal that growth covers — the rest is money you deposit yourself, including growth on your starting amount.
Most savings questions run backwards: the target and the deadline are fixed, and the unknown is the monthly deposit. This calculator solves the annuity formula in reverse — instead of projecting what a deposit grows to, it finds the deposit whose growth lands exactly on your target. Any current balance you enter is first grown forward to the target date at your rate, and only the remaining gap is spread across the deposits.
Interest does part of the work, and the calculator shows how much. On a $10,000 target over 3 years at 6%, the deposits sum to $9,151.92 and growth supplies the remaining $848.08 — which is why the required deposit, $254.22, is less than the naive 10,000 / 36 = $277.78. At a 0% rate there is no help from growth and the deposit is exactly the target divided by the months, as the second formula states.
The plan assumes deposits at the end of each month and a steady rate throughout. If your deadline is close, the rate barely matters and the answer is dominated by target divided by months; if the deadline is years away, small rate differences move the required deposit noticeably. Running the calculator at a cautious rate and an optimistic rate gives a realistic range for the deposit to budget.
Enter it as the current balance. The calculator grows that balance forward at your rate to the target date and only asks deposits to cover the shortfall. Money already saved counts for more than its face value precisely because it has the whole period to grow.
Because each deposit earns interest for the time it is in the account. On the $10,000, 3-year example at 6%, growth contributes $848.08 of the target, so your deposits only need to supply the other $9,151.92 — $254.22 a month instead of $277.78. The longer the period and the higher the rate, the bigger this discount.
The required deposit approaches target divided by months, and if the deadline is this month it is simply the full remaining amount. There is no shortcut in the maths: with almost no time for growth, nearly all of the target must come from deposits. The calculator reports this plainly rather than dressing it up.
The solver works in monthly deposits because that matches most pay cycles and savings habits. If you save weekly or per paycheque, the monthly figure still gives you the budget target: divide by about 4.33 for a weekly amount. The underlying formula is the same; only the period length changes.
No. It is arithmetic: given a target, a date and a rate you supply, it solves for the deposit. It does not recommend a target, a savings account or a rate, and the rate you enter is your assumption — actual account rates vary and can change during the saving period.
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