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Calculators/Retirement & Investing
Compound Interest Calculator
See how your money grows exponentially over time — the most powerful force in personal finance.
$
$
%
years
Growth Summary
Total Contributed$130,000
Interest Earned$213,778
Future Value$343,778
Interest Multiple2.64x
Future Value
$343,778
Total Contributed
$130,000
Interest Earned
$213,778
How to Use This Calculator
1
Enter your starting balance
The amount you have right now to invest. Even $1,000 matters — Einstein allegedly called compound interest the 8th wonder of the world.
2
Enter monthly contributions
How much you plan to add each month going forward. Consistent contributions are the #1 factor in long-term wealth. Even $200/month makes a massive difference over 30 years.
3
Enter the annual rate of return
The S&P 500 has averaged ~10% annually (7% inflation-adjusted). Use 6–7% for a conservative estimate, 8–10% for a historical average, 12%+ only for aggressive estimates.
4
Set the time horizon
Time is your biggest lever. At 8%, money doubles every ~9 years (Rule of 72). The difference between investing for 20 vs 30 years can be life-changing.
5
Choose compounding frequency
Monthly compounding (12x/year) is standard for most investments. Daily (365) is used for savings accounts. Annual is used for some bonds. More frequent = slightly more growth.
Real-World Examples
The $500/Month Rule
Starting Balance
$5,000
Monthly Contribution
$500
Annual Return
8%
Time Horizon
30 years
Result$734,000+
Total contributed: $185,000. Interest earned: $549,000+. Your money makes more than you do after year 18.
Late Start — Age 40
Starting Balance
$25,000
Monthly Contribution
$1,500
Annual Return
7%
Time Horizon
25 years
Result$1,170,000+
It's never too late. Aggressive saving ($1,500/mo) from age 40 still builds over a million by retirement at 65.
Frequently Asked Questions
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