There's a famous story that when Albert Einstein was asked what he believed was the most powerful force in the universe, he replied "compound interest." Whether or not he actually said that, the message is true. Compound interest is the reason why investing early and consistently can turn modest savings into life-changing wealth over time.
Our Compound Interest Calculator shows you exactly how your money grows month by month. Enter your principal amount, an expected annual return, and the number of months you plan to invest for. The calculator shows your monthly investment requirement, total interest earned, and the final value of your investment.
How Compounding Works
Simple interest pays you returns only on your original investment. Compound interest pays returns on your original investment plus on the returns you've already earned. It's interest on interest. This compounding effect is what creates exponential growth. The longer your money stays invested, the more dramatic the effect becomes.
For example, $10,000 invested at 8% annual returns with monthly compounding grows to about $14,898 after 5 years. Keep it there for 20 years, and it becomes $49,268 - even without adding a single extra dollar. With monthly contributions, the numbers become truly impressive.
The Rule of 72
Want to know how long it takes to double your money? Divide 72 by your annual interest rate. At 8% returns, your money doubles every 9 years. At 12%, every 6 years. This is a quick mental shortcut that investors use all the time.
Privacy for Your Financial Planning
Your investment goals and financial situation are deeply personal. Our calculator runs entirely in your browser. Your principal amounts, interest rates, and investment timelines never leave your device. No data collection, no tracking, no ads based on your financial activity.