Compound Interest
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (which is only calculated on the original amount), compound interest makes your money grow exponentially over time. It works for you when you're saving an
Compound Interest Definition
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (which is only calculated on the original amount), compound interest makes your money grow exponentially over time. It works for you when you're saving and against you when you're borrowing.
Compound Interest in Practice — Example
A freelance designer deposits $10,000 into a business savings account earning 4% APY, compounded monthly. After year one, she has $10,407 — not just $10,400, because each month's interest earns interest in subsequent months. After 5 years without adding another dollar, she has $12,210. After 10 years: $14,908. The same $10,000 at simple interest would only be $14,000 after 10 years. That extra $908 came purely from compounding — interest earning interest.
Why Compound Interest Matters for Your Business
Compound interest is the most powerful force in finance for building wealth — and the most dangerous force when you're in debt. Understanding it changes how you think about both saving and borrowing.
On the savings side, compound interest rewards patience. Business reserves parked in a high-yield account grow faster than you'd expect, especially over multiple years. The earlier you start building reserves, the more compounding works in your favor. Even modest deposits add up significantly over time.
On the debt side, compound interest is why credit card balances spiral out of control. A $10,000 balance at 24% APR compounded daily grows to $12,712 in just one year if you make no payments. Understanding this motivates faster debt repayment and smarter borrowing decisions.
How Compound Interest Works
Compound Interest Formula:
``
A = P(1 + r/n)^(nt)
``
Where:
Compounding frequency matters:
| $10,000 at 5% for 10 years | Final Amount |
|---|---|
| Annually (n=1) | $16,289 |
| Quarterly (n=4) | $16,436 |
| Monthly (n=12) | $16,470 |
| Daily (n=365) | $16,487 |
More frequent compounding = more growth, though the difference between monthly and daily is minimal.
Compound Interest vs Simple Interest
Simple interest is calculated only on the original principal: $10,000 at 5% always earns $500/year, every year. Compound interest is calculated on principal plus accumulated interest, so each period earns slightly more than the last. Over short periods, the difference is small. Over years or decades, compound interest dramatically outperforms simple interest. Savings accounts, CDs, and most loans use compound interest.
FAQ
Q: How does APY relate to compound interest?
A: APY (Annual Percentage Yield) already accounts for compounding. A 4% APY means you'll earn 4% over a year regardless of compounding frequency. APR (Annual Percentage Rate) doesn't account for compounding, so the actual yield may be higher than the stated APR.
Q: Can compound interest work against my business?
A: Absolutely. Any debt with compound interest — credit cards, some business loans, lines of credit — grows faster than you might expect if you only make minimum payments. Always understand whether your debt compounds and how frequently.
Related Terms
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Related Terms
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