Your assumptions
Try a simple scenario
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Tools · Calculator
Compounding-interest calculator in yen.
This is a simple way to explore how regular investing might grow over time. It is especially useful if you are thinking about NISA and want to see how steady monthly contributions can add up.
Estimated result
What this scenario suggests
Final portfolio value
¥0
Your ending balance after contributions and estimated growth.
Total contributions
¥0
The total amount you put in yourself over the period.
Total growth
¥0
The difference between your ending value and your own contributions.
This uses monthly compounding for a rough estimate. Real returns do not arrive smoothly, markets can fall as well as rise, and actual results will vary.
Plain-English note
What to pay attention to
In many simple long-term plans, the biggest early driver is not a spectacular return assumption. It is staying consistent long enough for compounding to have time to work.
If you are using this while thinking about NISA, try changing just one input at a time. A small increase in years or monthly contributions can make a surprisingly large difference.
Yearly breakdown
See how the estimate builds over time
Useful for separating your own contributions from estimated market growth.
| Year | Contributions to date | Estimated growth | Ending balance |
|---|
Reminder
Useful for planning, not prediction
This calculator is educational. It does not know your actual portfolio, fees, tax position, risk tolerance, or future market conditions.
A result that looks neat on a screen is still only an estimate. Please treat it as a way to think more clearly, not as a promise.
Next step
Want the wider context?
If the calculator helps and you want a calmer plain-English explanation of how NISA fits into a simple long-term plan, the main book and guide pages are the next place to go.
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