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Investment planning tool

Compound Interest Calculator

Estimate how an initial investment and regular contributions may grow over time, and compare compound interest with simple interest.

Compound interest calculation

Your inputs are calculated only in this browser and are not stored on a server.

USD
USD
%
years

This changes the display format only. The calculated numbers stay the same and no exchange rate is applied.

Calculation results

$72,022.06

Based on $46,000.00 contributed over 10 years, the estimated balance is $72,022.06.

Total contributions
$46,000.00
Estimated earnings
$26,022.06
Cumulative return
56.57%
Simple-interest balance
$65,495.00
Compound vs. simple difference
$6,527.06
Annual return used
7%

Year-by-year growth chart

Each bar is one year. The filled part is that year's balance: contributions at the bottom, earnings on top. When a year loses money, the amount lost is shown separately as a dashed box above the filled part.

  • Total contributions$46,000.00
  • Earnings$26,022.06
  • Balance (height of the filled part)$72,022.06

Year-by-year detail

On narrow screens the table scrolls sideways inside its own box.

Contributions, earnings and balance by year
YearTotal contributionsEarningsBalance
0$10,000.00$0.00$10,000.00
1$13,600.00$840.68$14,440.68
2$17,200.00$2,002.37$19,202.37
3$20,800.00$3,508.29$24,308.29
4$24,400.00$5,383.31$29,783.31
5$28,000.00$7,654.12$35,654.12
6$31,600.00$10,349.34$41,949.34
7$35,200.00$13,499.63$48,699.63
8$38,800.00$17,137.91$55,937.91
9$42,400.00$21,299.44$63,699.44
10$46,000.00$26,022.06$72,022.06

How to use the compound interest calculator

  1. Enter your initial principal and optional regular contribution.
  2. Choose an expected annual return, whole-year period, and compounding frequency.
  3. Select whether contributions are made at the beginning or end of each period, then calculate.

Formula and variables

Without contributions, the calculator uses A = P(1 + r/n)^(nt). A is the ending balance, P the principal, r the annual rate as a decimal, n the number of compounding periods per year, and t the number of years. Regular contributions are added at the selected time in each period.

Worked example

With $10,000 initially, $300 added at each month-end, a 7% annual return, monthly compounding, and 10 years, the calculator applies the monthly rate 120 times. Use the result panel to see contributions, estimated earnings, and annual balances separately.

Simple interest vs. compound interest

Simple interest earns a return only on each contribution. Compound interest also earns returns on earlier returns, so the gap generally grows with time. With negative returns, compounding can instead reduce the balance.

Display currency

The currency selector changes formatting only. It does not convert your amounts and no exchange rate is applied, so the numbers you type and the calculated results stay exactly the same.

Assumptions and limitations

  • The annual rate is divided by 12 for monthly compounding; it is not converted from an effective annual yield.
  • Calculations keep decimal precision internally and round only the displayed currency amounts.
  • Returns are estimates, not guarantees. Taxes, fees, inflation, and changing market returns are excluded.

Frequently asked questions

Can I enter a negative return?

Yes. Values above -100% and up to 500% are accepted.

Why can real results differ?

Actual returns vary over time, and products may apply fees, taxes, and different contribution or compounding rules.

Are my values stored?

No. The calculation runs in your browser and does not send or save your inputs.

Related calculators

Returns on money you invest and interest on money you borrow are the same compounding idea seen from two directions.