Compound Interest Calculator
Project investment growth with compound interest.
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About Compound Interest Calculator
How much does one deposit grow when each period's interest is added back and starts earning interest itself? Enter the starting amount, an annual rate, a whole number of years and how often interest compounds, from annually to daily. You get the final amount, the interest earned and a table with the opening balance, interest and closing balance for every year. The fields open with a worked example, so numbers are on screen before you type.
Features
- Five compounding frequencies from annual to daily
- Final amount, total interest and principal cards
- Year-by-year schedule for up to 100 years
- Opens on an editable worked example
- Clear messages when principal, rate or years are out of range
Limitations
- It models one lump sum only. There are no regular deposits or withdrawals, and taxes, fees and inflation are not included.
- The rate is a fixed nominal annual rate split across the compounding periods; daily compounding uses 365 periods a year.
- Principal must be above zero and no more than 1,000,000,000,000, the rate cannot be negative or above 100, and years must be a whole number from 1 to 100.
- Figures are projections from the formula, not a forecast of real returns.
How it works
- Enter the Principal, the starting amount in dollars.
- Type the Annual interest rate as a percentage, from 0 to 100.
- Enter the Number of years as a whole number from 1 to 100.
- Choose a Compounding frequency: annually, semi-annually, quarterly, monthly or daily.
- Read the Final amount, Total interest and Principal cards, which update as you type.
- Scroll the year-by-year table for the opening balance, interest and closing balance of each year.
Example input
$10,000 at 7% for 10 years, compounded monthlyFrequently asked questions
- Only a little, once the rate and the years are fixed. On 10,000 dollars at 7% for 10 years, annual compounding ends at $19,671.51, quarterly at $20,015.97, monthly at $20,096.61 and daily at $20,136.18, so going from annual to daily adds $464.67.
- Not in this tool, which models a single deposit. Because growth scales with the amount, you can run each deposit separately with its own number of years and add the final amounts together to approximate a series of deposits.
- Each year the opening balance is multiplied by (1 + r/n) raised to the power n, where r is the annual rate as a decimal and n the compounds per year, which matches A = P(1 + r/n)^(nt). The balance carried between years is not rounded; only the displayed figures are rounded to cents.
- Enter the nominal annual rate, the figure before compounding, because the tool applies compounding itself. An advertised APY already includes compounding, so typing it in with monthly or daily compounding would count the effect twice and overstate the result.
- The schedule is built one whole year at a time, so years must be whole numbers from 1 to 100. Principal is capped at one trillion, and above about 1e15 the amounts switch to a rounded exponent form because a standard number can no longer hold cents.