Compound interest means you earn interest on your interest as well as on the money you put in. This calculator shows how a starting amount grows over time at a fixed annual rate, with yearly, half-yearly, quarterly, monthly, daily or continuous compounding, and optional monthly contributions.
You get the future value, the total you deposited, the interest earned and the effective annual rate, plus a year-by-year chart and table. It is useful for savings accounts, fixed deposits, index-fund projections, retirement planning and showing children how saving early pays off.
How to use the Compound Interest Calculator tool
- Enter your initial investment. It can be 0 if you only make monthly deposits.
- Enter the expected annual interest rate or return.
- Enter the number of years and choose the compounding frequency.
- Add a monthly contribution if you will keep saving.
- Read the future value and check the growth chart and yearly table.
Why use ToolOrca Compound Interest Calculator
- Future value, total deposits and interest earned
- Six compounding frequencies, including continuous
- Monthly contributions
- Effective annual rate (APY)
- Stacked growth chart and yearly table
- Formula with your numbers filled in
The compound interest formula
Without deposits the balance after t years is A = P × (1 + r/n)n·t, where P is the principal, r the annual rate as a decimal and n the number of times interest is added per year. With continuous compounding it is A = P × er·t.
Worked example: $1,000 at 5% for 10 years grows to $1,628.89 with yearly compounding, $1,647.01 with monthly compounding and $1,648.72 with continuous compounding. More frequent compounding helps, but the rate and the time matter far more.
Monthly deposits are added at the end of each month and grow at the same rate. With the default values, $10,000 at 7% compounded monthly plus $200 a month for 10 years reaches about $54,714: $34,000 deposited and $20,714 of interest.
The rule of 72 and the power of time
To estimate how long money takes to double, divide 72 by the annual rate: at 6% it takes about 12 years, at 9% about 8 years. Starting early makes a big difference: $500 a month at 7% for 30 years grows to about $610,000, although only $180,000 was deposited.
Returns on investments such as shares are not fixed, so treat projections as illustrations. This calculator is for information only and is not financial advice.
Frequently asked questions
How much will $10,000 be worth in 20 years at 8%?
With yearly compounding, $10,000 × 1.0820 = $46,609.57. Monthly compounding gives a little more, about $49,268.
What is the difference between simple and compound interest?
Simple interest is paid only on the original amount; compound interest is also paid on interest already earned. $1,000 at 5% for 10 years earns $500 simple interest but $628.89 compounded yearly.
What is APY or effective annual rate?
The rate you actually earn in a year once compounding is included. A 12% rate compounded monthly gives an effective annual rate of 12.68%.
Are contributions added at the start or end of the month?
At the end of each month, which is the usual convention. Depositing at the start of the month would earn slightly more.
Does the calculator include tax or inflation?
No. Results are before tax and are not adjusted for inflation. They are estimates for information only, not financial advice.