Calculator
Compound Interest Calculator
Explore how your starting amount, regular contributions, time, and returns may work together.
Estimated future value
$300,851
After 20 years at an estimated 7% annual return.
$130,000
$170,851
This estimate is for educational purposes only and is not a guarantee of future results.
Methodology
How this calculator works.
The estimate combines the future value of your starting balance with the future value of a fixed monthly contribution stream. Each monthly deposit receives only the growth available after it is invested.
Core calculation
FV = P(1 + r)ⁿ + C × ((1 + r)ⁿ − 1) ÷ r
P is the initial investment, C is the monthly contribution, r is the monthly return, and n is the number of months. When r is zero, the contribution portion is C × n.
01
Set the period
The annual return is divided by 12 and the time horizon is converted into months.
02
Grow each amount
The initial balance compounds for the full period; later deposits compound for less time.
03
Separate the result
Total deposits are subtracted from the ending value to show estimated investment growth.
Important assumptions
- Returns are constant and compound monthly; real markets will vary from month to month.
- Contributions are made at the end of each month and remain unchanged.
- Taxes, platform fees, transaction costs, and withdrawals are not included.
- Inflation is not deducted, so the result is expressed in future nominal dollars.