Investment calculator
Explore potential growth based on your contributions and returns.
Explore a hypothetical investment balance from a starting amount, monthly contributions, assumed annual return and time period. You can enter negative growth to see a loss scenario.
Example calculation
Based on the example figures in the form. Enter your own details, then select Calculate.
Illustrative future balance
£47,161.58
- Starting amount
- £10,000.00
- Total paid in, including starting amount
- £34,000.00
- Investment growth
- £13,161.58
An estimate based on the assumptions below. For information only, not financial advice.
How this is calculated
Assumes a constant effective annual rate and contributions at the end of each month. Figures are before tax, fees and inflation. This is an illustration, not a forecast. Investments can fall in value, and you could get back less than you put in.
Calculation method
Future balance = P × (1 + r)ⁿ + C × ((1 + r)ⁿ − 1) ÷ r
P is the starting investment and C is the contribution added at each month’s end. The annual effective growth assumption is converted to a monthly rate r; n is the total number of months. At 0% growth, the balance is simply the starting amount plus all contributions.
Worked example
An initial £10,000 with no further contributions becomes £12,100 after two years at a constant 10% annual return. At −10% each year it becomes £8,100. Neither scenario accounts for charges, tax or inflation, and neither predicts market performance.
Method documented: · How we check calculations · Report an error
Common questions
What return should I assume?
The pre-filled rate is an example, not a recommendation or expected return. Compare several assumptions, including low or negative growth, and consider the risk and costs of the actual investment.
Does this reflect the ups and downs of markets?
No. Real returns vary and their order can affect outcomes when you contribute or withdraw money. This model applies the same monthly growth rate throughout.
Is the result adjusted for inflation or fees?
No. It shows a nominal balance before fees and taxes. Its purchasing power could be lower than the same amount of money today.