Compound Interest Calculator
See how your money grows over time with compound interest. Add regular contributions, choose your compounding frequency, and watch your investment grow — works for any country worldwide.
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What Is Compound Interest?
Compound interest is the process of earning interest not just on your original investment, but also on all the interest you have already accumulated. Often called the eighth wonder of the world, compound interest is the reason a small amount of money invested early in life can grow into a substantial sum over time. Unlike simple interest, which only calculates returns on your principal, compound interest snowballs with every passing period, turning modest contributions into meaningful wealth given enough time.
Whether you are saving in a TFSA or RRSP in Canada, a 401(k) or IRA in the USA, an ISA in the UK, a superannuation fund in Australia, or any savings account anywhere in the world, understanding compound interest helps you make smarter decisions about where to put your money and how long to leave it there. Our calculator works for any currency and any country. Select your local currency symbol, enter your numbers, and see your investment grow.
The frequency of compounding matters more than most people realize. Money compounded daily grows faster than money compounded monthly, which grows faster than money compounded annually, even at the exact same interest rate. Use the compounding frequency selector to see exactly how much difference it makes for your specific investment over your chosen time horizon.
Frequently Asked Questions
What is the Rule of 72? The Rule of 72 is a shortcut for estimating how long it takes to double your investment. Divide 72 by your annual interest rate and the result is approximately how many years until your money doubles. At 6% your money doubles in roughly 12 years, and at 9% it doubles in about 8 years.
What is the difference between end-of-period and beginning-of-period contributions? When you add a contribution at the beginning of the period it earns interest for that full period. When you add it at the end, it earns interest starting the following period. Beginning-of-period contributions produce slightly higher returns over time.
What annual return should I use? For a diversified stock index fund, historical averages suggest 7 to 10 percent annually. For a high-interest savings account, use your bank’s current rate. Many financial planners use 6 to 7 percent as a conservative long-term estimate for projections.
Does this calculator work for any country? Yes, completely. Compound interest is pure math. The calculator works identically whether you are in Canada, the USA, the UK, Australia, Germany, Nigeria, Brazil, or anywhere else in the world.