Free Online Calculators
Monthly savings + compound interest → final amount
If you invest a fixed amount every month — whether into an ETF, index fund, or savings account — your money grows in two ways: through your regular contributions and through compound interest on everything you've already accumulated. This investment calculator combines both factors to show you exactly where you'll stand at any future date.
For example, if you invest $300 per month at an average annual return of 7% for 20 years, you'll deposit a total of $72,000. But thanks to compounding, your end capital would grow to roughly $155,000 — meaning interest and returns account for more than $83,000 of that final balance. That's the power of a consistent savings plan over time.
The calculator shows three key figures: total end capital, total amount deposited, and total interest earned. Seeing all three together helps you understand not just where you'll end up, but how much of that growth you actually earned versus contributed yourself.
This tool is especially useful for DCA (Dollar Cost Averaging) investors — people who invest the same dollar amount regularly regardless of market conditions. DCA is a popular strategy for ETF investors because it removes the temptation to time the market. By investing consistently, you naturally buy more shares when prices are low and fewer when prices are high, smoothing out your average cost over time.
The compound interest savings effect becomes dramatically more powerful the longer you stay invested. Waiting just five extra years can double your end result in many scenarios. For instance, starting at age 25 versus age 30 with $200/month at 8% annual return produces roughly $702,000 versus $472,000 by retirement age — a $230,000 difference from just 60 extra monthly contributions.
At simple-calculator.online, this savings plan calculator is built to give you fast, clear projections without any financial jargon. You can adjust your monthly amount, interest rate, and time horizon in seconds to compare different scenarios side by side.
When entering your expected return rate, be realistic. A broad stock market ETF has historically averaged around 7–10% annually before inflation. Bond-heavy portfolios typically return 3–5%. For a conservative savings account or money market fund, 2–4% may be more appropriate. Using a rate that's too optimistic can lead to a plan that falls short in reality.
Also consider that this ETF calculator assumes a fixed monthly contribution and a constant annual rate — it doesn't account for taxes, fund fees, or market volatility. In practice, you might want to subtract 0.5–1% from your expected return to account for fund expense ratios and any applicable capital gains taxes.
Compound interest means you earn returns not just on your deposits, but on the interest and gains you've already accumulated. Each month, your growing balance generates more growth, which is why long investment horizons produce such dramatically larger results.
The calculator compounds interest monthly, which aligns with the frequency of your regular contributions. This gives the most accurate picture for a typical monthly savings plan or ETF investment strategy.
Yes — if you already have an existing balance, simply enter it as your starting amount. The calculator will factor in both that initial lump sum and your ongoing monthly deposits when projecting your future value.