Compound Interest Calculator
Compound Interest Calculator
What is Compound Interest?
Compound interest is interest calculated on both the original principal and the accumulated interest over time. It allows money to grow faster compared to simple interest because earnings generate additional earnings.
Compound Interest Formula
| Formula |
|---|
| A = P (1 + r/n)nt |
- A = Final amount
- P = Principal (initial investment)
- r = Annual interest rate (decimal)
- n = Number of compounding periods per year
- t = Time in years
How Compound Interest Works
Step-by-Step Example
You invest $1,000 at 10% annual interest for 2 years.
- Year 1: $1,000 × 10% = $100 → Balance = $1,100
- Year 2: $1,100 × 10% = $110 → Balance = $1,210
Total Amount = $1,210
Compound Interest vs Simple Interest
| Feature | Simple Interest | Compound Interest |
|---|---|---|
| Interest Base | Principal only | Principal + interest |
| Growth Type | Linear | Exponential |
| Returns | Lower | Higher over time |
Compounding Frequency
The more frequently interest is compounded, the faster your money grows.
- Annually (once per year)
- Semi-annually (twice per year)
- Quarterly (4 times per year)
- Monthly (12 times per year)
- Daily (365 times per year)
Example of Compounding Frequency Impact
| Compounding Type | Rate | Final Amount (Example $1,000 for 2 years at 6%) |
|---|---|---|
| Annual | 6% | $1,123.60 |
| Daily | 6% | $1,127.49 |
Rule of 72
| Formula |
|---|
| Years to Double ≈ 72 ÷ Interest Rate |
Example: At 8% return, money doubles in about 9 years (72 ÷ 8 = 9).
Continuous Compounding
| Formula |
|---|
| A = P × ert |
Continuous compounding represents the maximum theoretical growth when interest is calculated at every instant.
Advantages of Compound Interest
- Fast wealth growth over time
- Rewards long-term investing
- Helps savings grow automatically
Disadvantages of Compound Interest
- Increases debt quickly for borrowers
- Credit cards can become expensive
- Requires time to see benefits
Real-Life Uses
- Savings accounts
- Certificates of Deposit (CDs)
- Retirement accounts (401k, IRA)
- Investment portfolios
FAQs
What is compound interest in simple words?
It is interest earned on both your original money and the interest already earned.
Why is compound interest powerful?
Because it grows money exponentially over time.
Is compound interest good or bad?
It is good for saving and investing but increases loan costs.
What is the main difference between simple and compound interest?
Simple interest uses only principal, while compound interest includes accumulated interest.
Conclusion
Compound interest is one of the most important concepts in finance. It helps savings grow faster and also explains why long-term debt becomes more expensive.
References
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