Compound Interest Calculator
Harness the exponential mathematics of compound growth. This calculator demonstrates how initial capital combined with disciplined recurring deposits multiplies over multi-year horizons.
Starting investment or opening savings balance
Recurring monthly contribution added to principal
Expected annualized interest or investment yield
Number of years funds remain invested
How often accrued interest compounds into balance
Total accumulated balance after compounding
How to Use This Calculator
- Enter your starting deposit in the Initial Principal field.
- Set your budgeted recurring deposit in Monthly Contribution.
- Specify expected annualized return (e.g. 7% to 10% for broad-market index funds).
- Drag the investment horizon slider to your target timeframe.
- Observe how compounding interest increasingly overtakes contributions over time.
Formula & Calculation Methodology
Total accumulated value includes principal multiplied by exponential rate periods, plus the future value of a recurring annuity stream.
Worked Example
$10,000 initial balance, $500 monthly deposit at 7% annual yield over 10 years
Frequently Asked Questions
What is the Rule of 72 and how does it relate to compounding?↓
The Rule of 72 is a mental shortcut to estimate how quickly money doubles. Divide 72 by your annual rate of return: at an 8% annual return, your capital doubles approximately every 9 years (72 ÷ 8 = 9).
How does compounding frequency impact returns?↓
More frequent compounding (e.g., daily or monthly vs annually) generates slightly higher returns because interest is credited and begins generating its own return sooner. However, annual return rate and time horizon have a far larger impact than frequency alone.
Does this calculator account for inflation or capital gains taxes?↓
This calculation reflects nominal returns before taxes, inflation, or advisory expense ratios. To model real purchasing power, subtract expected inflation (~2.5% to 3%) from your nominal interest rate.
Can compound interest work against me on debt?↓
Yes. Compound interest works identically on revolving credit card debt and compounding loans, causing unserviced interest to accumulate exponentially onto the principal balance.
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Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.