Compound Interest Calculator
See what your savings grow into, with or without regular contributions
- 元本合計
- ￥58,000
- 利息総額
- ￥86,572.72
| 年数 | 元本合計 | 最終残高 |
|---|---|---|
| 5 | ￥22,000 | ￥28,494.83 |
| 10 | ￥34,000 | ￥54,713.58 |
| 15 | ￥46,000 | ￥91,881.93 |
| 20 | ￥58,000 | ￥144,572.72 |
すべての処理はブラウザ内で完結します。データが端末外に送信されることはありません。
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使い方
Compound interest means you earn returns on your returns. This calculator applies that period by period and adds any recurring contribution at the end of each period, which is how savings accounts and retirement plans actually credit deposits.
Enter your starting amount
The balance you already have. Leave it at zero if you are starting from nothing and only contributing monthly — the calculator handles that case.
Set an expected annual return
Use a rate you can defend. Savings accounts run low single digits; a broad stock index has historically averaged around 7% after inflation, but with years that are far worse and far better.
Choose the time horizon and compounding frequency
Years is where the real leverage is — doubling the horizon does far more than doubling the rate. Compounding frequency matters much less than most people expect, usually a fraction of a percent.
Add a monthly contribution
Recurring deposits usually dominate the outcome for anyone starting with a modest balance. The results split total contributions from total interest so you can see which is doing the work.
使用例
Starting from 10,000 with 200 a month
10,000 invested at 7% for 20 years with 200 added monthly grows to roughly 143,000. Of that, about 58,000 is money you deposited and roughly 85,000 is compound growth — the growth overtakes the contributions around year 14.
Why starting earlier wins
Contributing 300 a month at 7% for 30 years reaches about 366,000. Waiting ten years and contributing 600 a month for the remaining 20 years — twice the monthly amount — reaches only about 313,000. The extra decade beats the extra money.
このツールについて
Project the future value of an investment or savings account with compound interest. Set a starting amount, expected return, time horizon and optional monthly contribution to see your final balance and exactly how much of it is growth rather than money you put in. Everything is calculated in your browser.