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Compound Interest Calculator
Watch a starting balance and monthly contributions compound over decades — principal, contributions, and growth split apart.
New to this? Start here
This shows what happens when your money earns money. Set what you have now and what you can add each month — the chart shows how much of your future balance comes from growth rather than saving. Drag Years or Annual return to see how much faster growth takes over.Final balance
$854,537
after 30 years
You put in
$190,000
Growth did
$664,537
350% of what you contributed
By year 8, growth is adding more per year than you are — your money out-earns your saving.
ContributionsGrowth
View as table
| Year | Contributed | Growth | Balance |
|---|---|---|---|
| 0 | $10,000 | $0 | $10,000 |
| 5 | $40,000 | $11,637 | $51,637 |
| 10 | $70,000 | $43,669 | $113,669 |
| 15 | $100,000 | $106,088 | $206,088 |
| 20 | $130,000 | $213,778 | $343,778 |
| 25 | $160,000 | $388,915 | $548,915 |
| 30 | $190,000 | $664,537 | $854,537 |
Methodology & assumptions
- Interest compounds monthly; contributions are added at the end of each month.
- The annual return is applied as a constant rate — real markets vary year to year (see the Monte Carlo simulator for sequence risk).
- Contribution step-up is applied once per year.
- Results are nominal (not inflation-adjusted) and pre-tax.
Educational only
This simulator is for education. It uses simplified assumptions, is not financial, tax, or investment advice, and no result here is a prediction or a recommendation. Talk to a licensed professional before acting.More retirement & compounding tools
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