See how a lump sum and regular monthly saving grows over time with reinvested returns — in an ISA, pension or investment account. Free PDF projection.
This calculator is a guide only and not financial advice. It assumes a constant annual return for illustration; real investment returns vary and can be negative. The value of investments can fall as well as rise. Past performance does not predict future results.
Compound interest is the engine behind almost every long-term investment. Instead of earning a return only on the money you put in, you also earn returns on the returns already added — so your pot grows faster and faster the longer you stay invested. This free calculator shows exactly how a starting lump sum plus regular monthly contributions could grow over time, and how much of your final pot is your own money versus compound growth.
Enter your starting amount, how much you can add each month, the annual return you expect and how many years you will stay invested. You can also model an annual increase in your contributions as your income rises. The results update instantly, and the free PDF shows a year-by-year breakdown plus the striking difference that starting just five years earlier can make.
Compounding is most powerful inside a tax wrapper. Returns in a Stocks & Shares ISA or a pension grow free of UK income and capital gains tax, and a Lifetime ISA even adds a 25% government bonus on top. For shorter goals, compare the latest regular saver rates.