See how a lump sum and monthly contributions could grow over time. Try a few different growth rates; nothing here is a promise of what you'll actually get.
A lump sum you're investing now, enter 0 if you're starting from scratch.
These are example rates to compare scenarios, not a prediction of what any investment will actually return.
A typical platform and fund charge might sit somewhere around 0.5–1%, but check your own provider's actual figure.
Based on the details you've entered
How the estimate builds year by year
The most commonly quoted example is the S&P 500, a US index tracking 500 of the largest listed American companies. Since 1928, it's averaged around 10% a year including dividends: or roughly 7% a year once adjusted for inflation, which is the more useful figure for understanding actual buying power over time.
That average hides a lot of movement. In any single year, the S&P 500 has returned anywhere from over +40% to below −35%; very few individual years land anywhere near the long-term average itself. The figure only becomes meaningful over long periods, typically a decade or more, where the strong years and the weak years even out.
Two things worth keeping in mind: this is a US index, so it isn't a stand-in for how a UK-based fund or the FTSE 100 has performed, which has its own, generally lower, long-term average. And past performance is exactly that: past. It doesn't guarantee what any index will return in future.
This is part of why the three scenarios above are deliberately more cautious than simply quoting "the S&P 500 average": they're a range to compare, not a single number to expect.
This calculator assumes your starting amount and monthly contributions grow at a steady annual rate, compounded monthly, for the whole period: real investments don't move in a straight line, they go up and down along the way. The three preset scenarios are just examples to compare, not a prediction of what any specific investment will do.
For how investing actually works more broadly, see our Investing, actually explainer.
This calculator gives an illustrative estimate based on the figures and growth rate you choose; it isn't a forecast, a guarantee, or personalised advice. The value of investments can fall as well as rise, and you could get back less than you invest. For guidance specific to your situation, a regulated financial adviser can help.