Project how your investments could grow over 5, 10, 20, or 30+ years. Understand what drives growth, what realistic UK returns look like, and why fees matter more than you think.
An investment growth calculator projects how your portfolio could grow over time based on three inputs: your starting amount (lump sum), your regular contributions (monthly or annual), and the expected annual return rate. It applies compound interest — earning returns on your returns — to show the projected value at different time horizons.
The key output is the future value of your investments, broken down into how much you contributed from your own money versus how much came from investment growth. This breakdown is eye-opening: over long periods, compound growth often contributes more than your own contributions. On a 30-year investment at 7%, roughly 60-70% of the final value is compound growth rather than money you put in.
Our calculator also shows inflation-adjusted (real) returns, so you can see what your future pot would be worth in today's money. This is crucial for realistic planning — £500,000 in 30 years will buy significantly less than £500,000 today.
Compounding is exponential — it accelerates over time. £200/month at 7% grows to £69,300 after 15 years, £172,000 after 25 years, and £405,000 after 35 years. Notice the pattern: the first 15 years produce £69,300, but the next 10 years add £102,700, and the final 10 years add £233,000. The later years do the heavy lifting.
For most people, monthly contributions drive the majority of the final value. Doubling your contribution from £200 to £400/month roughly doubles your outcome at any time horizon. Increasing contributions by even small amounts — £25 or £50 more per month — has a significant compounding effect over decades.
The difference between 5% and 8% average returns may sound small, but over 25 years it is enormous. £300/month at 5% for 25 years gives roughly £179,000. At 8%, the same contributions give approximately £285,000 — over £100,000 more. However, higher returns typically come with higher volatility and risk.
Investment fees compound against you. A platform charging 0.45% plus a fund fee of 0.5% (total 0.95%) will cost significantly more over time than a platform with no fee and a fund at 0.07% (total 0.07%). On a £200,000 portfolio over 20 years, this difference amounts to tens of thousands of pounds lost to fees instead of compounding in your favour.
| Asset class | Nominal return | Real return (after inflation) | Volatility |
|---|---|---|---|
| Cash savings | 4-5% | 1-2% | None |
| UK gov bonds (gilts) | 3-5% | 0-2% | Low-Medium |
| UK equities (FTSE 100) | 6-8% | 3-5% | Medium-High |
| Global equities | 7-10% | 4-7% | Medium-High |
| S&P 500 | 8-10% | 5-7% | Medium-High |
Returns are approximate long-term historical averages and are not guaranteed. Cash savings rates reflect the current environment and may decrease. Equity returns assume reinvested dividends. Past performance does not guarantee future results.
High fees (1.0%)
~£386,000
Net of £114,000 in fees
Low fees (0.2%)
~£448,000
Net of £24,000 in fees
Difference
£62,000
Lost to higher fees
Based on £500/month contributions over 25 years at 7% gross returns. The high-fee scenario nets 6% after fees; the low-fee scenario nets 6.8%. Figures are illustrative.
Investment growth calculators produce illustrative projections, not guarantees. Real-world investment returns fluctuate — some years you might gain 20%, other years you might lose 15%. The calculator smooths this into a constant average, which is useful for planning but does not reflect the bumpy reality of actual investing.
Use the results to compare scenarios and understand the broad shape of your financial future. Ask questions like: "What is the difference between saving for 20 years versus 30 years?" or "How much more would I have if I increased my contribution by £100/month?" These relative comparisons are highly valuable even if the absolute numbers are approximate.
For the most realistic view, always check the inflation-adjusted figure in the calculator. A projection of £500,000 in 30 years sounds impressive, but adjusted for 2.5% inflation, it is worth roughly £295,000 in today's money. This is still excellent — but it sets appropriate expectations.
Project your investment growth with our free calculator.
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Capital at risk. This is not financial advice. Affiliate link — we may earn a commission at no extra cost to you.
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