Compound Interest Calculator
Albert Einstein allegedly called compound interest the "eighth wonder of the world." Whether he said it or not, the math is genuinely astonishing. See what consistent investing can do over time — with your actual numbers.
Your Investment Details
Final Balance
$691,150
Total Contributed
$190,000
Total Growth
$501,150
Where Your Balance Comes From
Year-by-Year Breakdown
| Year | Balance | ||
|---|---|---|---|
| Year 1 | $16,919 | +$919 | $16,000 |
| Year 5 | $49,973 | +$3,148 | $40,000 |
| Year 10 | $106,639 | +$6,968 | $70,000 |
| Year 15 | $186,971 | +$12,383 | $100,000 |
| Year 20 | $300,851 | +$20,061 | $130,000 |
| Year 25 | $462,290 | +$30,945 | $160,000 |
| Year 30 | $691,150 | +$46,374 | $190,000 |
This calculator is for educational purposes only. Past market performance does not guarantee future results. Actual returns will vary.
Understanding the results
The 7% assumption
7% is a commonly used conservative estimate for long-term stock market returns, after adjusting for inflation. The historical average is closer to 10% nominal.
Why monthly matters
Monthly contributions beat annual lump sums because your money starts compounding sooner. Automation makes this effortless — set it and forget it.
The time multiplier
Starting at 25 vs 35 can mean $400,000+ more at retirement — even investing the same amount. Time is the most powerful variable in the equation.