📊 Compound Interest Calculator
⚠️ This calculator provides estimates for educational purposes. Actual investment returns vary and are not guaranteed. Past performance does not indicate future results. Consult a qualified financial advisor before making investment decisions.
What Is Compound Interest?
Compound interest is the interest you earn on both your original deposit and on the interest that has already accumulated. Unlike simple interest — which only pays on the principal — compound interest creates a snowball effect where your money grows faster over time.
Albert Einstein reportedly called compound interest the "eighth wonder of the world" — and for good reason. The longer your money compounds, the more dramatic the growth becomes.
The Compound Interest Formula
The standard formula for compound interest is:
A = P × (1 + r/n)^(n×t)
Where:
- A = Final amount (future value)
- P = Principal (initial deposit)
- r = Annual interest rate (as a decimal)
- n = Number of times interest compounds per year
- t = Number of years
Example Calculation
If you invest $10,000 at a 5.5% annual rate compounded quarterly for 10 years:
A = $10,000 × (1 + 0.055/4)^(4×10) = $10,000 × (1.01375)^40 ≈ $17,275
You'd earn approximately $7,275 in interest — and that's without adding any extra money along the way.
How Compounding Frequency Affects Growth
The more frequently interest compounds, the faster your money grows:
- Annually: Interest added once per year
- Quarterly: Interest added 4 times per year
- Monthly: Interest added 12 times per year
- Daily: Interest added 365 times per year (maximum growth)
The difference between annual and daily compounding on a $10,000 investment over 10 years at 5.5% is approximately $127. While this seems small, the gap widens significantly with larger sums and longer timeframes.
Tips to Maximize Compound Interest
- Start early: Time is the most powerful factor. A 25-year-old who invests $200/month can accumulate more than a 35-year-old investing $400/month by retirement.
- Reinvest dividends: In the US and Canada, dividend reinvestment plans (DRIPs) automatically compound your stock market returns.
- Use tax-advantaged accounts: In the US, Roth IRAs and 401(k)s allow tax-free compounding. In Canada, TFSAs offer similar benefits. In the UK, ISAs shield your gains from tax. In Australia, superannuation accounts benefit from concessional tax treatment.
- Avoid early withdrawals: Breaking the compounding cycle resets your progress. Even small withdrawals can cost thousands in lost future growth.
Regional Notes
- US: High-yield savings accounts (HYSA) currently offer 4-5% APY. CDs lock in rates for fixed terms.
- Canada: GICs (Guaranteed Investment Certificates) provide compound interest with government backing.
- UK: Fixed-rate bonds and Cash ISAs offer tax-free compounding up to £20,000/year.
- Australia: Term deposits and high-interest savings accounts offer competitive compounding rates.