Compound interest is the most powerful force in personal finance. When your investment earns returns that are themselves reinvested to earn more returns, the effect accelerates over time. Use this free compound interest calculator to see exactly how your money grows.
🧮 Compound Interest Calculator
Why Compound Interest Is the Investor’s Best Friend
The difference between earning simple interest and compound interest might seem small in the first few years, but over decades the gap becomes staggering. A $10,000 investment at 7% annually becomes roughly $76,000 after 30 years with compound interest — without adding another dollar.
The key variables are your rate of return, the compounding frequency, and most importantly, time. Starting 10 years earlier can result in twice the ending balance, even with identical contributions. This is why financial advisors universally agree: start investing as early as possible, even with small amounts.
Use our best index funds guide to find low-cost investments to put inside your compound interest machine.