Investment Calculator
Project an investment's growth from a starting amount, regular contributions and an expected yearly return.
About the Investment Calculator
Enter what you start with, how much you add each month or year, an expected yearly return and how many years. The calculator shows the ending balance and splits it into what you paid in and what came from growth, with a chart of the balance over time.
The return is treated as an effective yearly rate, converted exactly to the contribution frequency. Real markets vary year to year, so use a cautious long-run average and try a lower rate too.
The formula
Each period: balance × (1 + r)^(1/k) + contribution
- r
- expected yearly return as a decimal
- k
- contributions per year (12 for monthly)
- contribution
- amount added each period
Worked example
20,000 to start, 500 a month, 7% a year for 20 years
- Paid in: 20,000 + 500 × 240 = 140,000
- Ending balance: about 331,162
- Growth: 191,162, more than everything paid in
Things to keep in mind
- Assumes the same return every year; real returns rise and fall, and the order matters when you add or withdraw money.
- Before tax, fees and inflation unless you use a net, after-inflation rate.
Questions people ask
What return should I assume?
A long-run figure for your mix of investments, after fees; 5–7% after inflation for a diversified stock portfolio is often used.
Does this include tax?
No; taxes depend on the account and country.
How do I see the result in today's money?
Use a return after inflation, for example 7% minus 3% inflation ≈ 4%, and the balance is in today's purchasing power.