Portfolio Growth Calculator
Project an investment portfolio from a starting balance plus regular contributions that can rise each year, and see how much of the result is your money versus growth.
A portfolio grows from three things: what you start with, what you keep adding, and the returns those balances earn over time. This calculator projects the future value of a starting balance and ongoing contributions, with an optional yearly increase to what you contribute, and splits the result into the total you put in versus the growth on top. For compounding frequency, inflation, and tax options, see the compound interest calculator.
Assumptions
- The return is constant for the whole period and the number of years is treated as a whole number. The starting balance compounds annually; contributions are converted to an exact effective rate per contribution period from the same annual return, so monthly or annual contributions reconcile to the rate you enter.
- Contributions are made at the end of each period. The yearly increase steps up the contribution once per year: the first year uses the base amount, and the increase applies from the second year onward, compounding year over year. Within a year the contribution is level.
- Total contributed is your starting balance plus the nominal sum of every contribution, with no time-value adjustment. Total growth is the future value minus that total.
- All figures are nominal (not adjusted for inflation), before any taxes or investment fees. For an inflation-adjusted or after-tax view, and for sub-annual compounding choices, use the compound interest calculator.
- Not modeled: variable or negative returns and sequence-of-returns risk (one steady rate is used, not real market swings), fees and expense ratios, and taxes. Every result is rounded to the nearest cent.
- This is an estimate for educational purposes only, not financial advice. Real returns vary year to year, and your actual results will differ.
How it works
A portfolio’s future value is two pieces added together: the growth of what you start with, and the growth of everything you contribute along the way.
The starting balance compounds at the annual return: starting times (1 + return)^years.
The contributions are a recurring stream, so they grow as an annuity. The annual return is first
converted to an exact effective rate per contribution period, rPer = (1 + return)^(1/k) − 1, where k
is the number of contributions per year (12 for monthly, 1 for annual). The future value of n level
contributions is then contribution times ((1 + rPer)^n − 1) / rPer.
If you choose a yearly contribution increase, each year’s contributions step up by that percentage. The stream becomes a growing annuity at the year level: the first year’s contributions are valued as a one-year annuity, and each later year’s value grows by the raise, handled by a single growing-annuity formula so nothing is approximated.
Total contributed is your starting balance plus the nominal sum of every contribution. Total growth is the future value minus that total.
Worked example
Start with $10,000, add $500 a month, assume a 7 percent annual return, and let it run 20 years.
- Starting balance grows to $10,000 times 1.07^20 = about $38,697.
- The $500 monthly contributions grow as an annuity at the effective monthly rate, to about $253,768.
- Future value: about $292,465.
- Total contributed: $10,000 + ($500 times 240) = $130,000.
- Total growth: about $162,465, more than the money you put in.
That split, growth exceeding contributions over a long horizon, is the whole point of investing early and consistently.
Scope and limitations
The return is treated as constant, which a real market never is, and all figures are nominal (before inflation, taxes, and fees). For an inflation-adjusted or after-tax view, or to vary the compounding frequency, use the compound interest calculator. To see what a future balance is worth in today’s dollars, use the inflation calculator. This is an estimate for education, not financial advice.
Sources
- U.S. SEC, Investor.gov: compound interest and how investments grow
- U.S. SEC, Investor.gov: saving and investing basics
- Standard time-value-of-money formulas (future value of a lump sum and of an ordinary/growing annuity).
Frequently asked questions
- How is this different from the compound interest calculator?
- This tool is a focused portfolio projection: a starting balance, contributions that can rise each year, and a single return, split into what you contributed versus the growth. The compound interest calculator adds choices for compounding frequency, an inflation-adjusted value, and a tax on gains. Use this one for a quick projection and that one for the detailed options.
- Why does the contribution increase matter so much?
- Because raising your contribution each year adds money during the years it has the longest to compound. Even a small annual increase, such as bumping contributions with your pay raises, can lift the ending value meaningfully over a long horizon, since each higher contribution still earns returns for many years.
- What return should I assume?
- There is no correct number, since real returns vary every year. Many people use a long-run average for a diversified stock portfolio as a rough planning figure, but the actual path will be bumpy and could be lower. Try a range of returns to see how sensitive the result is rather than trusting one figure.
- Are these future dollars or today's dollars?
- Future, nominal dollars. The projection does not adjust for inflation, so the ending value will buy less than the same number of dollars today. To see the result in today's purchasing power, use the compound interest calculator's inflation-adjusted value or the inflation calculator.
Related calculators
Learn how this works
New to this topic? Our companion guide explains it in plain language: How Much Should I Invest Each Month to Reach My Goal?
Last reviewed June 2026.