Compound Interest Calculator
Calculate how your money grows with compound interest. Enter the initial deposit, the monthly contribution, the interest rate and the time period to see the future value, the total invested, the interest earned and a year-by-year breakdown.
- Future value
- $42,566.51
- Total invested
- $25,000.00
- Interest earned
- $17,566.51
| Year | Total invested | Accumulated interest | Balance |
|---|---|---|---|
| 1 | $3,400.00 | $208.11 | $3,608.11 |
| 2 | $5,800.00 | $677.03 | $6,477.03 |
| 3 | $8,200.00 | $1,432.84 | $9,632.84 |
| 4 | $10,600.00 | $2,504.23 | $13,104.23 |
| 5 | $13,000.00 | $3,922.76 | $16,922.76 |
| 6 | $15,400.00 | $5,723.14 | $21,123.14 |
| 7 | $17,800.00 | $7,943.56 | $25,743.56 |
| 8 | $20,200.00 | $10,626.02 | $30,826.02 |
| 9 | $22,600.00 | $13,816.73 | $36,416.73 |
| 10 | $25,000.00 | $17,566.51 | $42,566.51 |
What is compound interest?
With compound interest, the interest earned each period is added to the balance and starts earning interest too. That is the famous “interest on interest”. The longer the period, the faster your money grows, and the effect is much stronger in the final years of the investment.
Compound interest formula
Without contributions, the future value is A = P × (1 + r)ⁿ, where P is the principal, r is the rate per period and n is the number of periods. With monthly contributions, each deposit earns interest for as long as it stays invested, and the calculator compounds month by month.
To convert an annual rate into the equivalent monthly rate, use (1 + annual rate)^(1/12) − 1. A 12% annual rate is about 0.95% per month, not 1%.
Compound interest example
$1,000 invested at 1% per month, with contributions of $100 per month, grows to $2,395.08 in 12 months: $2,200 invested and $195.08 in interest.
IMPORTANT: this simulation does not account for taxes, fees or inflation, and past returns do not guarantee future results. It is not investment advice.
Frequently asked questions
What is the compound interest formula?
A = P × (1 + r)ⁿ, where A is the final amount, P the principal, r the rate per period and n the number of periods. With contributions, each deposit earns interest for as long as it stays invested.
What is the difference between simple and compound interest?
With simple interest, interest is only charged on the initial amount. With compound interest, it is applied to the accumulated balance, including previous interest, so your money grows faster over time.
How do I convert an annual rate to a monthly rate?
Use (1 + annual rate)^(1/12) − 1. For example, 12% per year is about 0.95% per month. The calculator does this conversion when you choose an annual rate.
Does the simulation include taxes?
No. The result is gross, without income tax, fees or inflation. The net amount depends on the type of investment and the time period.