Compound Interest
Calculate compound interest on investments and savings
Compound Interest Calculator projects how savings grow when returns are reinvested — including optional regular contributions — so you can compare scenarios before committing to a plan.
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How to Use
- Enter the principal amount
- Set the annual interest rate
- Choose the compounding frequency
- Enter the time period in years
- View total amount and interest earned
Features
- Multiple compounding frequencies
- Principal and interest breakdown
- Visual growth chart
- Flexible time periods
- Compare different rates
Tips for getting Compound Interest right
- Match the compounding frequency field to reality: most savings accounts compound daily or monthly, bonds usually annually
- Small rate differences dominate long horizons — test 6% vs 7% over 30 years and compare endings
- Contribution timing matters; this tool applies contributions at each compounding step
Formulas used
Lump sum: A = P(1 + r/n)^(nt). With recurring contributions the tool compounds step-by-step each period, adding the contribution before interest is applied — the same convention banks use for monthly deposit plans.
Worked example
- $10,000 invested once at 7% compounded annually
- After 10 years: A = 10,000 × 1.07^10 ≈ $19,671
- The $9,671 of growth came entirely from reinvested returns — no extra deposits
Why frequency changes the answer
The more often interest compounds, the more times each year's growth starts earning its own interest. The difference is small at moderate rates but grows with rate and time — over 30 years at 10%, monthly compounding beats annual by thousands.
| Compounding | $10,000 @ 7%, 10 years |
|---|---|
| Annually | $19,671 |
| Quarterly | $20,097 |
| Monthly | $20,197 |
| Daily | $20,234 |
Frequently Asked Questions
What compounding frequencies are supported?
How does compounding frequency affect returns?
Can I add regular contributions?
Privacy & Security
Projection math runs locally in your browser. Financial figures never leave your device.
Tips & Best Practices
- Match the compounding frequency field to reality: most savings accounts compound daily or monthly, bonds usually annually
- Small rate differences dominate long horizons — test 6% vs 7% over 30 years and compare endings
- Contribution timing matters; this tool applies contributions at each compounding step
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