What Is Simple Interest?
Simple interest is calculated only on the original principal amount. That means the interest does not build on top of previous interest.
Because of that, growth is more predictable and linear.
What Is Compound Interest?
Compound interest is calculated on both the original amount and the accumulated interest from previous periods. That creates faster growth over time.
In simple terms, you start earning interest on your interest.
Why the Difference Matters
The gap between simple and compound interest becomes much more visible over longer periods of time. A small difference in the early years can grow into a large difference later.
Simple Interest Example
If you invest or borrow $1,000 at 5% simple interest, the interest is based only on that original $1,000 each period.
Compound Interest Example
If the same $1,000 compounds, each period builds on the previous one. The balance grows more quickly because the new interest is being calculated on a larger amount.
When You Usually See Simple Interest
- Some short-term loans
- Certain educational examples
- Basic financial calculations
When You Usually See Compound Interest
- Savings accounts
- Investing growth projections
- Many longer-term financial products
Compounding Frequency Matters Too
Interest can compound annually, monthly, daily, or at other intervals. More frequent compounding can increase growth further, even when the rate stays the same.
Final Thoughts
If you are saving or investing, compound interest is one of the most powerful tools available over time. If you are borrowing, compounding can also make costs grow faster than expected.
Understanding the difference helps you compare options more confidently.