How savings with regular deposits grow
This calculator models two engines at once: your opening balance compounding, plus a stream of monthly deposits that each compound from the day they land. The combined formula is FV = initial·(1+i)N + deposit·(((1+i)N − 1) ÷ i), where i is the monthly rate (annual rate ÷ 12) and N is the total number of months. When the rate is 0%, it simplifies to initial + deposit × N. The same compounding engine powers our compound interest calculator for lump sums.
How to use this calculator
Enter your initial amount, the monthly deposit you plan to add, the annual interest rate, and the number of years. The result shows your projected balance, how much of it you contributed yourself, and how much is interest. Consistency is the key variable — small monthly amounts compound into surprisingly large sums over time. If you have a target amount and a deadline, the savings goal calculator works backwards to the deposit.
Worked example
Start with $1,000, add $100 every month, and earn 5% annually for 10 years. Your monthly rate is 0.05 ÷ 12 ≈ 0.004167 over 120 months, giving a future balance of about $17,175. You contributed $13,000 ($1,000 start + $12,000 in deposits), so roughly $4,175 is interest.
| Years | Contributed | Balance |
|---|---|---|
| 5 | $7,000 | $8,098 |
| 10 | $13,000 | $17,175 |
| 20 | $25,000 | $42,210 |
These figures are an estimate for general information only and are not financial advice; consult a qualified professional before making money decisions. Compare accounts on equal terms using the APY calculator.
Frequently asked questions
- How much will I save in 10 years?
- Starting with $1,000 and adding $100 a month at 5% interest, you would have about $17,175 after 10 years, of which roughly $4,175 is interest.
- Does this assume monthly compounding?
- Yes. The calculator compounds interest monthly and assumes each deposit is added at the end of the month and starts earning the following period.
- What if the interest rate is 0%?
- With no interest, your balance is simply the initial amount plus all deposits: initial + monthly deposit × number of months.
- Why is my contribution less than the final balance?
- The difference is interest. Your money and each deposit earn compound interest over time, so the balance exceeds what you put in.
- What if I deposit at the start of each month?
- Your balance ends up slightly higher, because every deposit earns one extra month of interest. On a $100 monthly deposit at 5% over 10 years the gap is only around $70, so the projection here stays a close estimate either way.