Investment Return Calculator (UK)
Project how your investments could grow over time with compound interest and regular monthly contributions.
Your details
The lump sum you are starting with today.
How much you plan to add each month.
A long-term average growth rate. 4–5% is a commonly used cautious estimate.
Your results
Your figures appear here as you fill in your details.
This calculator is for educational purposes only and does not constitute financial advice. Returns are hypothetical and do not reflect actual investment performance. Inflation, fees, and taxes are not accounted for. For personalised advice, please consult a qualified financial adviser.
How this works
Each month we apply growth to your running balance, then add your monthly contribution:
- Interest is added first — your current balance grows by one month's share of the annual return.
- Then your contribution goes in — so each month's deposit starts earning from the following month.
We repeat this every month for the whole investment period. Total contributions is your initial investment plus every monthly deposit, and investment growth is whatever your final value is over and above what you put in.
Assumptions
- Growth is a constant annual rate, applied monthly. Real returns vary year to year and can be negative.
- Returns are hypothetical and do not reflect actual investment performance.
- Inflation, fees, and taxes are not accounted for.
- Contributions are assumed to stay level for the whole period.
Last updated . Figures are UK-specific — check current rates on GOV.UK before acting.