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Free Financial Calculator

Compound Interest Calculator

Calculate how your money can grow with compound interest, regular contributions, taxes and inflation. Compare your contributions with the estimated investment growth over time.

Investment Details

$
Amount invested at the beginning.
$
Optional amount added regularly.
%
Use a constant estimated annual rate for this projection.
%
%

Projection Results

Estimated Future Value
$106,639.02
Before estimated tax
Total Contributions
$70,000.00
Interest Earned
$36,639.02
Estimated Tax
$5,495.85
After-Tax Value
$101,143.16
Today’s Purchasing Power
$79,012.88
Effective Annual Rate
7.23%
Growth Multiplier
1.52×
Estimated Growth Over Time 10 years
Compound interest growth chart Estimated investment value over time.
Estimated balance

How Compound Interest Works

Compound interest is interest earned on both your original investment and the interest that has already accumulated. Because the accumulated earnings can themselves earn returns, growth can accelerate over longer periods.

This calculator combines an initial investment with optional recurring contributions. It lets you choose how often interest compounds and how frequently additional money is contributed.

For the initial investment: FV = P × (1 + r/n)^(n×t)

Recurring contributions are separately grown from their contribution date to the end of the investment period.
P
Initial investment
r
Annual interest/return rate as a decimal
n
Compounding periods per year
t
Investment period in years
Contribution
Amount added at each selected contribution interval
Inflation
Estimated annual loss of purchasing power

Compound Interest Example

Suppose you start with $10,000, add $500 every month, earn an estimated 7% annual return, and remain invested for 10 years. With monthly compounding and contributions made at the end of each month, the calculator estimates the future balance before tax and inflation.

The exact result changes when you change the contribution frequency, contribution timing, return rate, compounding frequency, tax assumption or inflation assumption.

Important: A calculator projection is a mathematical estimate based on the assumptions entered. Actual investment returns can vary substantially over time.

Year-by-Year Growth

The table below shows how your estimated balance changes over the investment period. It separates the amount contributed from the estimated investment growth.

Year Contributed Estimated Interest Estimated Balance
Total — — —

When to Use a Compound Interest Calculator

Long-Term Savings

Estimate how an initial deposit and recurring savings could grow over several years.

Retirement Planning

Explore how different contribution amounts and assumed returns can affect a long-term savings projection.

Investment Comparisons

Compare hypothetical rates, time periods and contribution schedules using consistent assumptions.

Savings Goals

See how regular deposits may contribute to reaching a future financial target.

Inflation Planning

Compare a future nominal balance with an estimated value expressed in today’s purchasing power.

Contribution Strategies

Test monthly, quarterly and annual contribution schedules to understand their projected effect.

Related Financial Calculators

Future Value Calculator

Calculate the future value of an investment using periodic deposits and growth assumptions.

Calculate Future Value →

CAGR Calculator

Calculate the compound annual growth rate between an initial and final investment value.

Calculate CAGR →

Frequently Asked Questions

What is compound interest?
Compound interest is interest calculated on an original amount plus previously accumulated interest. Over time, this can produce growth on both the original principal and earlier earnings.
What is the difference between interest and compounding frequency?
The annual interest rate describes the assumed yearly rate, while the compounding frequency describes how often interest is added to the balance. For example, monthly compounding applies the periodic rate 12 times per year.
Does contributing monthly increase compound growth?
Regular contributions can increase the final balance because each contribution has additional time to earn returns. The result depends on the contribution amount, timing, return rate and investment period.
Should contributions be made at the beginning or end of a period?
Contributions made at the beginning of a period have more time to earn a return than contributions made at the end. This calculator lets you model either assumption.
What happens if the interest rate is 0%?
No investment interest is generated. The final balance is simply the initial investment plus the contributions, subject to the other assumptions in the calculator.
Does inflation reduce the value of my future money?
Inflation can reduce purchasing power. The calculator therefore provides an estimated today’s-money value by discounting the after-tax result using the selected inflation assumption.
Does this calculator predict investment returns?
No. It is a mathematical projection based on a constant assumed rate. Real investments can experience gains, losses, changing rates, fees, taxes and other factors that are not fully represented by this model.
Is tax calculated exactly?
No. The tax field is a simplified planning assumption applied to the calculated interest. Actual tax treatment depends on the investment, account type, jurisdiction, holding period and applicable tax rules.
Important financial disclaimer: This calculator provides mathematical estimates for educational and planning purposes only. It does not guarantee investment performance and is not financial, tax or investment advice. Actual returns may differ because of market performance, changing interest rates, fees, taxes, timing and other factors.