The snowball effect: what could your investments be worth?

Growth can earn growth

Compounding begins when a return is added to your investment and later returns apply to the larger amount. Contributions create the base, investment performance changes it, and time allows the process to repeat.

Real markets move unevenly, sometimes sharply. A smooth annual percentage is useful for an illustration, while a range of assumptions gives a more honest view of uncertainty.

Starting earlier changes the workload

Consider two hypothetical investors. Sarah contributes £200 a month from age 25 to 35, then leaves the money invested until 65. James starts at 35 and contributes £200 every month until 65.

At an illustrative 7% effective annual return before fees, Sarah contributes £24,000 and could finish with roughly £262,000. James contributes £72,000 and could finish with roughly £235,000. Sarah’s early contributions had three extra decades to compound. The result is an illustration and real returns will vary.

The four forces behind the result

Contributions are the money you add. Returns describe how the investments change in value. Fees reduce the balance that remains invested. Inflation reduces the purchasing power of the future total.

• Contribute: regular additions build the base that can compound.
• Return: higher assumed growth creates a wider range of future outcomes and should never be treated as guaranteed.
• Fees: a recurring percentage charge applies to an expanding balance, so a small annual difference can become substantial.
• Inflation: a future pound may buy less; viewing results in today’s money makes long-term plans easier to interpret.

Use ranges, not a single forecast

A central estimate can anchor the discussion. A lower and higher scenario show how dependent the outcome is on returns. Including fees and inflation keeps the headline figure connected to the amount you may actually be able to spend.

For money needed within a few years, investment volatility may make cash more suitable. Longer horizons provide more time to recover from falls, but they never remove risk.