simple interest
Interest calculated only on the original principal amount, without including previously accumulated interest — less powerful than compound interest over time.
Example
“Simple interest on a $1,000 loan at 10% is $100 per year regardless of duration — unlike compound interest which grows.”
Memory Tip
SIMPLE interest = same dollar amount each period. No interest on interest. Weaker than compound.
Why It Matters
Simple interest matters because it helps you understand the true cost of borrowing or the real returns on savings. Many loans and bonds use simple interest calculations, so knowing how it works protects you from underestimating what you will actually owe or earn over time.
Common Misconception
People often think simple interest and compound interest produce similar results, but they diverge significantly over longer periods. Simple interest only grows linearly while compound interest grows exponentially, making compound interest far more powerful for long-term wealth building.
In Practice
If you borrow $1000 at 5 percent simple interest per year for 3 years, you pay $50 in interest each year (1000 times 0.05 equals 50), totaling $150 in interest. With compound interest at the same rate, you would pay $157.63 because interest gets calculated on the growing balance, not just the original principal.
Etymology
SIMPLE (straightforward, not compounded) INTEREST. INTEREST calculated SIMPLY on the original amount.
Common Misspellings
Learn personal finance fundamentals free
Related Terms
More in fundamentals
Other fundamentals terms you should know
Need financial definitions?
Clear definitions for 2,500+ finance, insurance, and investing terms.