Compound interest is often described as "interest on interest" because it includes interest earned on the initial principal as well as all interest accumulated over time. This compounding effect can significantly increase your savings or investments over the long term.
When interest compounds, you earn interest on:
The formula for compound interest is:
A = P(1 + r/n)^(nt)
Where:
Compound interest becomes more powerful over time. The longer your money compounds, the faster it grows. This is why starting to save and invest early is so important for building wealth.
Interest can compound at different frequencies: daily, monthly, quarterly, or annually. The more frequently interest compounds, the more your money will grow, though the difference is often small.
A simple way to estimate how long it will take for your money to double is the "Rule of 72." Divide 72 by the annual interest rate to approximate the number of years required for your investment to double.
For example, at a 6% annual return, your money would double in approximately 72 รท 6 = 12 years.
Banks typically compound interest daily or monthly on savings accounts, though the interest rates are often low.
Investments like stocks, bonds, and mutual funds can generate compound returns through price appreciation and reinvested dividends or interest.
The long-term nature of retirement accounts makes them perfect for harnessing the power of compound interest, especially when contributions are made regularly over decades.
Compound interest also applies to debt, particularly credit cards. When you don't pay your balance in full, interest compounds on both the principal and previously accrued interest, potentially leading to a debt spiral.