Simple vs. Compound Interest: How Much the Difference Really Is
A direct numeric comparison of simple and compound interest on the same principal, rate, and term, and why the gap grows over time.
Simple and compound interest start from the same formula building blocks — principal, rate, time — but produce meaningfully different results because of one key difference: whether interest itself earns more interest.
Head-to-head on the same numbers
| Method | $5,000 at 5% for 3 years |
|---|---|
| Simple interest | $750 interest → $5,750 total |
| Compound interest (annual) | ≈$788 interest → ≈$5,788 total |
The roughly $38 gap here comes entirely from the third year's interest being calculated on a balance that already includes the first two years' interest, under compounding. Extend the term to 20 years or raise the rate, and this gap widens dramatically — compounding is why long-term investing and long-term debt both grow far faster than a flat rate multiplication would suggest.
Compare your own numbers
Run the same principal, rate, and term through the Simple Interest Calculator and the Compound Interest Calculator side by side to see the exact gap for your situation.