A compound interest calculator shows Canadians the true power of investing early and consistently. Compound interest is the process of earning interest on both your original principal and on all previously accumulated interest, creating exponential growth over time. How Compound Interest Works for Canadian Investors: When you invest $10,000 at 7% annual interest compounded monthly, you earn $700 in the first year. In the second year, you earn 7% on $10,700, generating $749. Each year the base grows and so does the interest earned. Over 30 years, that single $10,000 investment becomes approximately $81,000 with no additional contributions. Add $300 monthly and it grows to over $380,000. The Rule of 72 for Quick Mental Math: The Rule of 72 is a simple mental shortcut for estimating how long it takes your money to double. Divide 72 by the annual interest rate to get the approximate doubling time in years. At 6% annual return, your money doubles in approximately 12 years. At 8%, it doubles in 9 years. At 4%, it takes 18 years. This simple rule helps Canadians quickly compare investment options and understand the long-term impact of higher returns. TFSA and RRSP Compound Growth in Canada: The best environment for compound growth is inside a Tax-Free Savings Account or Registered Retirement Savings Plan. Inside a TFSA, all growth is completely tax-free forever. Every dollar of interest, dividend, and capital gain compounds without the annual drag of taxation. A TFSA maxed out each year from age 18 at a 7% average annual return can grow to over $1,000,000 by retirement age. The Cost of Waiting to Invest: Someone who starts investing at age 25 with $300 per month at 7% will have approximately $900,000 at age 65. Someone who waits until age 35 to start the same contributions will have only approximately $440,000 — less than half — simply because they missed 10 years of compounding. This gap illustrates why starting early is the single most powerful factor in long-term wealth building for Canadians. Best Canadian Investments for Compound Growth: Low-cost index ETFs tracking the broad Canadian and global stock markets available through Questrade and Wealthsimple Trade offer the most accessible and cost-efficient way to harness compound growth. The Canadian couch potato portfolio strategy of simple index fund investing has consistently outperformed most actively managed Canadian mutual funds over 10 and 20 year periods after fees are accounted for. Starting your TFSA contributions at age 18 with even modest amounts and never interrupting the compounding process is the most reliable path to significant wealth accumulation for Canadians over a working lifetime.