Investment Growth Calculator
How long should I be invested for?
The longer you invest in equities (stocks and shares) the greater the probability that you'll get a positive return on your investment.
Investments can change in value a lot over a short period of time, both positively and negatively. Research by Schroders found that if you invested for a month, you would have lost money roughly 40% of the time in real (inflation-adjusted) terms.
However, if you had invested for longer, the odds would shift dramatically in your favour. On a five-year horizon, that figure falls to 20%. At 10 years it is approaching 10%. At 20 years it is negligible – of the 1,551 rolling 20-year periods between January 1871 and March 2020, there was only one where stocks lost money in real terms (July 1901- June 1921, when the real return was -0.2% a year).
You might think that you don't have 20+ years to invest, but the reality is that if you aim to retire by 60, the average life expectancy is 84 (men) or 87 (women), meaning you're likely to have 20 years of investing in retirement alone. If you're not retired yet, then that only adds to the length of time you have and therefore increases the likelihood of investing in equities providing a positive outcome.
At Wilfredson's, we work with you to work out how much money you'd need, and therefore how much you need to save, and for how long and what level of risk is right for you. Contact us today for a free, no obligation chat.
Why do we estimate growth rates like this?
Our central assumption of 5% a year matches the intermediate rate the FCA prescribes for pension and investment illustrations, although it is slightly more realistic (in our opinion) as we default to a 3% inflation rate compared to 2% by the FCA, which would provide a real return of 2% rather than 3% which the FCA states.
We adjust returns by risk level on a linear scale for simplicity but it is also backed by data. The high risk assumption of 7% a year comes from the full 125-year history in the Global Investment Returns Yearbook, where annualised real returns were 5.2% for worldwide equities, which would be greater than a 7% nominal return. On the other end, a low risk portfolio is likely to be primarily bonds and gilts which provided 1.7% real return and thus higher than 3% nominal return.
The optimistic and pessimistic figures either side are not forecasts of a best or worst case. Real returns have been both better and considerably worse than this range over shorter periods.
Is this calculator financial advice?
No. It shows what a given rate of return would produce over a given period. It is arithmetic, not a forecast, and is based on a number of assumptions which might not be representative of future returns.
The value of investments and the income from them can fall as well as rise, and you may get back less than you invested. Past performance is not a reliable indicator of future results.
This projection assumes a constant rate of return. Real investment returns vary year to year, and the order in which good and bad years occur materially affects the outcome, particularly once you begin drawing money out. The figures shown are not adjusted for charges, taxes and platform costs all of which will effect returns.
This calculator does not take account of your personal circumstances, objectives or attitude to risk, and does not constitute a personal recommendation.
Levels, bases of and reliefs from taxation are subject to change and depend on individual circumstances.
Wilfredson's Limited is an Appointed Representative of New Leaf Distribution Limited, which is authorised and regulated by the Financial Conduct Authority (FRN: 460421).
Citations:
Primary data
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Dimson, Marsh & Staunton, UBS Global Investment Returns Yearbook (2026 edition, data to end-2025). Free public summary at ubs.com. Now in its 26th edition, covering 126 years across 35 markets. FCA
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Dimson, Marsh & Staunton (2002), Triumph of the Optimists: 101 Years of Global Investment Returns, Princeton University Press
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Barclays Equity Gilt Study (2026 edition), UK data from 1899
Secondary data
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Schroders (2020), "The data that shows a case for long-term investing", https://www.schroders.com/en-gb/uk/individual/insights/the-data-that-shows-a-case-for-long-term-investing/
Peer-reviewed
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Mehra & Prescott (1985), "The Equity Premium: A Puzzle", Journal of Monetary Economics
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Fama & French (2002), "The Equity Premium", Journal of Finance — argues the expected premium is materially lower than the realised one
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Pástor & Stambaugh (2012), "Are Stocks Really Less Volatile in the Long Run?", Journal of Finance
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Bodie (1995), "On the Risk of Stocks in the Long Run", Financial Analysts Journal
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Siegel (1992), "The Equity Premium: Stock and Bond Returns Since 1802", Financial Analysts Journal
Regulatory
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FCA COBS 13 Annex 2 (projections)
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FCA COBS 4.6 (future performance in financial promotions) — the rule most likely to apply to a website calculator
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FCA (2017), Rates of Return for FCA Prescribed Projections
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FCA InvestSmart; MoneyHelper "Should I save or invest?"