The Power of Compound Interest: A Beginner's Guide
Learn how compound interest can grow your savings exponentially and why starting early matters more than investing large sums.
Simple vs Compound Interest
Simple interest is calculated only on the original principal amount. If you invest $1,000 at 5 percent simple interest, you earn $50 every year regardless of how long the money stays invested. After 10 years, you have $1,500. Compound interest, by contrast, calculates interest on the principal plus all previously earned interest. After the first year you have $1,050 and earn 5 percent on that larger amount the next year. After 10 years of compound interest at 5 percent, your $1,000 grows to $1,628.89, not $1,500.
The Rule of 72
The Rule of 72 is a mental math shortcut that tells you approximately how many years it will take for an investment to double at a given annual interest rate. Simply divide 72 by the interest rate.
Why Starting Early Matters
The most powerful aspect of compound interest is that time is the dominant variable, not the amount you invest. Someone who invests $200 per month starting at age 25 will typically end up with more money at retirement than someone who invests $400 per month starting at age 35, even though the late starter invests twice as much per month.
Compounding Frequency
How often interest is calculated and added to your balance affects the final amount, though the differences are smaller than most people expect. Annual compounding calculates interest once per year. Monthly compounding divides the annual rate by 12 and applies it each month. Daily compounding divides by 365. The more frequently interest compounds, the more you earn, but the incremental benefit decreases with each step.
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