Comparison page
Compound vs Simple Interest: Differences, Formula and Examples
This page has been rebuilt to support both educational search intent and calculator intent. The old version was directionally right but too thin. This version is more explicit about where the difference comes from, when it matters and which tool to use next.
Short answer
Simple interest grows on the original principal only. Compound interest grows on principal plus earlier interest.
That single difference is why compound interest usually pulls further ahead the longer money stays invested.
Side-by-side comparison
| Feature | Simple interest | Compound interest |
|---|---|---|
| Growth base | Original principal only | Principal plus prior interest |
| Growth pattern | Linear | Accelerating over time |
| Best use | Quick baseline or some loan structures | Savings and long-term investing |
| Effect of time | Steady increase | Increasing gap as years pass |
Worked example
Start with $5,000 at 7% for 15 years.
| Model | Approx. ending value |
|---|---|
| Simple interest | $10,250 |
| Compound interest, yearly | About $13,793 |
| Compound interest, monthly | About $14,245 |
The key lesson is not the exact cents. It is that compound interest gets stronger the longer the balance stays invested.
When to use each one
- Use simple interest for a quick baseline. It helps beginners see the difference without extra moving parts.
- Use compound interest for savings and investing questions. That is closer to how long-term growth really behaves.
- Use a contribution-aware calculator if you are adding money regularly. Neither a simple-interest baseline nor the basic compound formula tells the full story there.