Project your investment returns and track compound growth over time
Historical stock market average: 7-10%
£300,851
£130,000
£170,851
131.4%
Year 5
£49,973
Year 10
£106,639
Year 15
£186,971
Year 20
£300,851
Investing consistently over time is one of the most reliable ways to build long-term wealth. Whether you are putting money into a Stocks and Shares ISA, a general investment account, or a fund through your employer, understanding how your money could grow helps you set realistic targets and stay motivated. This investment growth calculator shows you the projected value of your portfolio over time, including the powerful effect of compound returns.
The single most important variable in long-term investing is time. Thanks to compounding — where your returns generate their own returns — a portfolio that grows for 30 years will massively outperform the same contributions made over 15 years, even if the monthly amount invested is identical. The earlier you start, the more time compound growth has to work in your favour. This calculator makes that effect visible, so you can see what a difference starting today versus in five years actually means in pounds.
Use this tool to model different scenarios: what if you increased your monthly contribution by £100? What if you achieved a 7% annual return instead of 5%? What if you started with a £10,000 lump sum? Experimenting with these variables gives you a practical sense of the levers available to you and helps you set an investment strategy that fits your goals and timeline.
The calculator uses compound interest with regular contributions. The formula accounts for an initial lump sum (if any) and monthly contributions, both growing at the specified annual return rate, compounded monthly. Each month, the existing portfolio value grows by the monthly rate (annual rate divided by 12) and any new contribution is added. This is the standard model for projecting investment growth used by financial planners.
All projections are estimates based on a constant rate of return. In reality, investment returns vary year to year — stock markets go up and down. The figures shown do not account for inflation, tax on gains, or investment fees, all of which reduce real-world returns. Use a conservative annual return assumption (5–7% is typical for a diversified equity portfolio over the long term) and treat the output as a guide, not a guarantee.