Compound Interest
Calculator
See how your savings grow with compound interest, monthly contributions, and reinvested returns over time.
Compound Growth
Set your growth scenario
Total Contributed
$37,000.00
Interest Earned
+$186,733.73
Final Value
$223,733.73
Multiplier
6.05x
Compound Growth Projection
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Based on fixed annual returns compounded monthly. Actual returns vary. Not financial advice.
How Compound Interest Works
The Compound Interest Formula
Compound interest calculates returns on both your principal and previously earned interest, creating exponential growth over time.
Formula: A = P(1 + r/n)nt
P = principal · r = annual rate · n = compounds/year · t = years
The Power of Monthly Contributions
Adding regular monthly contributions dramatically increases your final balance. Each contribution earns its own compound returns from the date it's deposited.
Example: $1,000 + $100/mo at 10% for 30 years
Final value: $223,734 · Interest earned: $186,734
Rule of 72
A quick way to estimate how long it takes to double your money: divide 72 by the annual return rate. This gives you the approximate number of years to double.
At 10%: 72 ÷ 10 = ~7.2 years to double
At 7%: 72 ÷ 7 = ~10.3 years to double
Frequently Asked Questions
See Real Results
See how compound growth has played out in real investments over the years.