Compound Interest Calculator
See how your money grows exponentially over time. Compound interest is the secret behind every great fortune. Watch your wealth snowball as interest earns interest.
Understanding Compound Interest
Compound interest is often called the "eighth wonder of the world" because of its powerful effect on wealth building. Unlike simple interest, which only earns on your original investment, compound interest earns returns on your returns. Each year, your gains generate their own gains, creating exponential growth over time.
The key factors that determine your final balance are: starting amount, contribution rate, interest rate, and most importantly, time. A $10,000 investment at 7% grows to $76,000 in 30 years. Add $500/month contributions, and that same investment becomes over $640,000. The math favors those who start early and stay consistent.
Use this calculator to see how different scenarios play out. Try adjusting the time period to see why starting 10 years earlier makes such a dramatic difference. Notice how much of your final balance comes from interest versus your actual contributions.
73% of your final balance is pure interest.
The longer you let compound interest work, the more your money does the heavy lifting for you.
Final Balance
Total value after compounding
Total Contributions
Your money invested
Interest Earned
Free money from compounding
Growth Over Time
- Your Contributions
- Interest Earned
The Rule of 72
At 7% annual return, your money doubles every 10 years. This simple formula (72 ÷ rate) helps you quickly estimate compound growth without a calculator. Start early, stay consistent, and let time do the work.
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