If you invest $100 at 10%, you earn $10 in year one. In year two, you earn 10% on $110, which is $11. In year three, you earn 10% on $121, which is $12.10. The interest amount keeps growing because the base amount keeps growing.

Yes, but only slightly. More frequent compounding means interest is added to your balance sooner, so it starts earning its own interest sooner. The difference between monthly and daily is usually small compared to the impact of the interest rate itself.

It depends entirely on your interest rate and contributions. Use the calculator to plot your specific numbers. As a rule of thumb, at a 7% return, money doubles roughly every 10 years (The Rule of 72).

For the stock market (e.g., an S&P 500 index fund), historical averages are around 9-10% before inflation, or 6-7% after inflation. For high-yield savings accounts or CDs, use the currently advertised rate (often 3-5%).

Simple interest is calculated only on the principal amount. Compound interest is calculated on the principal amount AND the accumulated interest of previous periods.

Inflation erodes the purchasing power of money over time. If your investment grows by 8% but inflation is 3%, your 'real' return in purchasing power is only about 5%.

If you hold investments in a taxable brokerage account, you will owe capital gains tax when you sell, or income tax on dividends and interest annually. Tax-advantaged accounts like IRAs or 401(k)s let your money compound tax-free or tax-deferred.

A step-up contribution means you increase your regular investment amount over time—for example, increasing your monthly deposit by 5% every year as your salary grows. This drastically accelerates wealth building.

The biggest mistake is waiting too long to start. Because compounding is exponential, the money you invest in your 20s does exponentially more work than money invested in your 40s. Another mistake is ignoring fees and taxes.

The Rule of 72 is a quick mental math trick. Divide 72 by your expected annual return rate, and the answer is roughly how many years it will take for your money to double. (e.g., 72 / 8% = 9 years).

You cannot lose money in a guaranteed fixed-interest account like a CD or Savings Account (up to FDIC limits). However, if you are 'compounding' in the stock market, the market can go down, meaning your returns can be negative in the short term.

APY stands for Annual Percentage Yield. It is the effective annual rate of return taking into account the effect of compounding frequency. It is slightly higher than the nominal interest rate.

You can start by opening a high-yield savings account (HYSA), a Certificate of Deposit (CD), or a brokerage account to invest in index funds or ETFs.

Compare the interest rates. If your credit card debt costs 25% APY, you should pay that off immediately, as it is 'compounding against you.' If your mortgage is at 3%, investing at an expected 7% return often makes more financial sense.

Adding monthly contributions turns the calculation into the future value of an annuity. The earlier in the month/year you contribute, the more time that specific contribution has to compound.

Yes, Warren Buffett is famous for saying that his wealth comes from a combination of living in America, lucky genes, and compound interest. The vast majority of his wealth was accumulated after his 50th birthday due to the exponential curve of compounding.

For investors, 'continuous' or 'daily' compounding is mathematically the best. However, for most long-term stock market investors, modeling annual compounding provides a perfectly fine estimate.

They are 100% mathematically accurate for fixed-rate accounts. For stock market investments, they are only estimates, as real-world market returns are volatile and do not go up in a perfectly straight line.

The curve represents exponential growth. In the first few years, your balance grows mostly from your own contributions. In the later decades, your balance grows exponentially from the interest earning interest on itself.