Formula and calculation method
A = P × (1 + r / n)^(n × t). Interest earned = A − P.
Assumes the interest rate stays fixed, with interest reinvested. No contributions, taxes, withdrawals or early withdrawal penalties.
How to use interest calculator
- Set Principal / amount. The example below uses 100000.
- Set Annual interest rate (%). The example below uses 6.
- Set Years. The example below uses 5.
- Set Compounds per year. The example below uses 12.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Principal / amount
- 100000
- Annual interest rate (%)
- 6
- Years
- 5
- Compounds per year
- 12
- Future balance
- 134,885.01525493
- Interest earned
- 34,885.01525493
Inputs and results explained
Interest Calculator takes 4 inputs. Fill each one using the same units and conventions, then select Calculate.
- Principal / amount: a number from 0 to 1000000000000. The worked example uses 100000.
- Annual interest rate (%): a number from 0 to 100. The worked example uses 6.
- Years: a number from 0 to 100. The worked example uses 5.
- Compounds per year: a number from 1 to 366. Whole numbers only. The worked example uses 12.
The result panel reports Future balance and Interest earned, so you can see the whole outcome rather than a single figure.
Factors affecting your result
Assumes the interest rate stays fixed, with interest reinvested. No contributions, taxes, withdrawals or early withdrawal penalties.
Changing principal / amount changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the interest calculator work?
A = P × (1 + r / n)^(n × t). Interest earned = A − P.
What inputs does Interest Calculator need?
Enter principal / amount, annual interest rate (%), years, compounds per year. Read the unit labels; percentages are entered as ordinary percentages, not decimal fractions.
How should I interpret the interest calculator result?
Assumes the interest rate stays fixed, with interest reinvested. No contributions, taxes, withdrawals or early withdrawal penalties.
Are my interest calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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