Scenario 1
Lump sum investment
$10,000 at 7% annual return for 20 years → $38,697. The original $10k earned $28,697 in compound returns.
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Compound Interest Calculator
See the real power of compounding — and why starting early makes all the difference.
Adjust your inputs
Results update instantly as you type or drag.
0 – 10,000,000
$
0.0 – 50
%
Expected annual return or interest rate
0 – 100,000
$
Regular amount added each month
1 – 50
Quick insights
Total contributed
$58,000
Interest earned
$86,573
Quick answer
What is compound interest?
Compound interest is interest calculated on both the principal and accumulated interest. The formula is A = P(1 + r/n)^(nt), where n is the compounding frequency.
How it works
From inputs to result in four steps
A quick walkthrough of what this calculator does behind the scenes.
- 1
Enter your starting amount (principal).
- 2
Set the annual interest rate.
- 3
Add a monthly contribution if applicable.
- 4
Set the time period — see how the balance grows.
Formula
The math behind the number
No black box — here's exactly how the result is computed.
A = P × (1 + r/n)^(n×t)
Each period your balance grows by the interest rate — then that larger balance earns even more next period.
Examples
Real-world scenarios
See how the numbers play out for typical use cases.
Scenario 2
With monthly contributions
$1,000 starting + $200/month at 7% for 30 years → $227,000+. Regular saving dramatically amplifies growth.
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