Investment Calculator
Project how regular monthly investing plus an expected return builds wealth over time.
Content updated July 1, 2026
Projection only. Real returns vary and can be negative in any given year.
Consistent investing beats big one-off deposits for most people, because regular contributions ride out market ups and downs and give compounding decades to work. This investment calculator projects the future value of a portfolio you build up with a monthly contribution and an optional starting balance.
Choose an expected annual return and a time horizon to see the projected total, how much of it is your own money, and how much is investment growth. It's the fastest way to answer 'if I invest X a month, what could I have in 20 years?'
The Investment formula
FV = PMT × [ ((1 + r)ⁿ − 1) ÷ r ] + P × (1 + r)ⁿFV = future value · PMT = monthly contribution · r = monthly return (annual return ÷ 12, as a decimal) · n = number of months (years × 12) · P = starting balance. The first term grows your contributions; the second grows any lump sum you begin with.
Worked example
Invest $300 a month for 20 years at 7% a year, starting from zero. Here PMT = 300, r = 0.07/12 ≈ 0.00583, and n = 240, giving FV ≈ $156,000. Of that, $72,000 is your own money and roughly $84,000 is investment growth.
Why regular investing works
Investing a fixed amount every month is often called dollar-cost (or pound-cost) averaging. You automatically buy more units when prices are low and fewer when they're high, which smooths out your average purchase price and removes the temptation to time the market.
Because each contribution has its own runway to compound, money invested early does the most work. Increasing your monthly amount even slightly, or starting a few years sooner, has an outsized effect on the final figure.
Choosing a realistic return
Historically, broad global stock markets have returned roughly 6–8% a year on average over the long run before inflation — but with significant swings, including multi-year downturns. Bonds and cash return less. A diversified portfolio sits somewhere in between depending on your mix.
For planning, it's wise to use a conservative rate and treat the output as a projection, not a promise. Real returns (after inflation) are what determine future buying power, so consider running the numbers with a lower 'real' rate too.
Frequently asked questions
▶How much should I invest each month?
Enough to hit your goals without straining your budget or emergency fund. Many people aim for 10–20% of income, but the right number depends on your timeline and targets. Try a few amounts here to see the impact.
▶Is a 7% return guaranteed?
No. Investment returns vary year to year and can be negative. Long-run stock market averages have been in the high single digits before inflation, but the future is uncertain — use conservative assumptions.
▶How is the future value of monthly investing calculated?
It uses the future value of an annuity formula, which sums each monthly contribution plus all the growth it earns until the end of the period. Any starting balance is compounded separately and added on top.
▶What is dollar-cost averaging?
It's investing a fixed amount at regular intervals regardless of price. You buy more units when prices are low and fewer when they're high, which smooths your average cost and removes the pressure of timing the market.
▶Does this calculator account for inflation?
No — it shows the nominal projected value before inflation and tax. To gauge real buying power, run the numbers again using a lower 'real' return (your expected return minus inflation).
▶Lump sum or monthly — which grows more?
A lump sum invested earlier generally grows more because it compounds for longer, but few people have a large sum spare. Regular monthly investing is what most people can actually sustain, and it still builds substantial wealth over time.
Learn more
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Open calculator →Disclaimer: Investment Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.