How to use the Investment Calculator
The investment calculator shows how a starting sum plus regular monthly additions could grow at an assumed return.
Open the Investment Calculator →
What you need to enter
- Starting amount ($)
- Monthly addition ($)
- Years
- Annual return (%)
The formula
Future value = start × (1 + r)^n + monthly addition × ((1 + r)^n − 1) ÷ r, with r the monthly return and n the number of months.
Worked example
Using the default values in the calculator:
- Starting amount ($): 10000
- Monthly addition ($): 500
- Years: 20
- Annual return (%): 7
| End balance | $300,850.72 |
| Total invested | $130,000.00 |
| Total earnings | $170,850.72 |
Tips for better results
- Time matters more than size: starting earlier usually beats saving more later.
- Run low, medium and high return cases rather than trusting one number.
Common mistakes to avoid
- Treating the assumed return as guaranteed.
- Forgetting fees and taxes that reduce the real result.
Please note: Calculators and guides give general estimates, not financial, tax or investment advice. Real offers depend on your lender, location and personal situation. See our Disclaimer.