Calculate compound interest

Project a balance and interest earned when a fixed rate compounds on a schedule.

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ToolCompound Interest Calculator
Input
Output
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Preview

How it works

Future value follows A = P(1 + r/n)^(nt), where P is principal, r the annual rate, n compounding periods per year, and t years. Interest is A − P after the selected frequency is mapped to n.

  • Annual compounding is the initial frequency because n = 1 makes the relationship easy to inspect.
  • Default rate, term, and principal are an editable illustration, not a market forecast.

Worked example

10-Year Investment
Calculate compound interest on $10,000 at 7% for 10 years, compounded monthly
Input
											Principal: 10000
Rate: 7
Years: 10
Compounding: monthly
Output
												Principal: $10000.00
Annual Rate: 7.00%
Time: 10 years
Compounding: monthly

Final Amount: $20096.61
Total Interest: $10096.61

When to use this

Savings projections compare frequencies, classroom exercises derive future value, and debt models estimate interest before payments and fees.

Edge cases

  • A negative rate can produce a lower balance and is not automatically rejected if the base remains meaningful.
  • Changing frequency changes the result while nominal rate and term stay fixed.
  • Continuous compounding is not selectable and should not be silently approximated by daily compounding.