Compound Interest Calculator
See what today's dollar becomes in 30 years.
Time does the work. This shows you how much.
S&P 500 30-yr avg: 10% (nominal) · 7% (real, after inflation)
Bonds: 4% · High-yield savings 2026: 4-5%
| Year | Balance | Growth |
|---|---|---|
| 1 | $16,919 | $919 |
| 5 | $49,973 | $9,973 |
| 10 | $106,639 | $36,639 |
| 15 | $186,971 | $86,971 |
| 20 | $300,851 | $170,851 |
| 25 | $462,290 | $302,290 |
| 30 | $691,150 | $501,150 |
Compound interest is what turns a small monthly savings habit into real money, but only if you can see the math. This calculator shows what a starting balance plus monthly contributions grows into over decades of compounding at a given annual return rate. Use it to check whether your current savings pace hits your retirement number, or to see the cost of waiting five years to start.
- 01**Starting balance**: what you have today
- 02**Monthly contribution**: what you'll add each month
- 03**Annual return**: expected annual growth rate (7% is a common historical stock market average after inflation; 10% is nominal)
- 04**Years**: how long you'll compound
Historical returns (nominal, before inflation): S&P 500 30-year average ~10%. Bonds ~4%. High-yield savings ~4-5% in 2026. Adjust for your actual mix. For retirement projections, most planners use 7% after-inflation for a stock-heavy portfolio.
Retirement 401k Planning
Contribution projections, account balances by type, Social Security estimates, and a FIRE milestone calculator.
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