Compound Interest Calculator
Model portfolio growth with principal and monthly contributions.
Calculator Input
Result
- Average Monthly Invested
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- Projected Future Value
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- Projected Gain
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How to Use This Compound Interest Calculator Effectively
The compound interest calculator shows how starting balance, recurring contributions, return rate, and time work together. It is most useful when you compare scenarios instead of treating one return rate as a promise.
Try a baseline, conservative, and optimistic case. For example, compare $10,000 plus $300 monthly over 10 years at 3%, 5%, and 7%. The gap between results shows why time and assumptions matter. If you want to compare actual beginning and ending values, use the Investment Return Calculator.
This tool does not predict markets. It models math from your inputs, so fees, taxes, inflation, volatility, and product restrictions should be reviewed separately.
FAQ
What return rate should I use?
Use at least three rates: conservative, baseline, and optimistic. Do not rely only on the highest number.
Does compounding include taxes or fees?
No. Deduct fees and taxes separately if they apply to your product or account.
Why does time change the result so much?
Compounding gives earlier money more periods to earn returns, so longer timelines can widen the outcome gap.