Useful next calculations
Rates and sources
Compound growth assumes reinvested returns and no platform fees. Past performance is not a guide to future returns.
Source: FCA — Investment basics. Check the linked guidance and any live quote before acting.
When to use this calculator
- Before choosing between saving, investing or changing a contribution.
- When you want to compare cautious, base and optimistic return assumptions.
- When you need a projection before making a longer-term decision.
- When you want to see whether starting earlier or contributing more changes the outcome more.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Present Value (£) | £10,000 |
| Annual Interest Rate (%) | 6% |
| Years | 10 |
| Compounds Per Year | 12 |
For those figures the calculator returns:
- Future value: £18,193.97
- Present value: £10,000.00
- Total gain: £8,193.97
- Rate: 6.00%
- Years: 10
Method & assumptions
This calculator uses the standard future value formula, applying compound interest to either a one-off lump sum, regular contributions, or a combination of both. You can adjust the compounding frequency to match your investment product — annual compounding suits most stocks and shares investments and ISAs, while monthly suits savings accounts that compound interest monthly.
The calculator assumes a fixed rate of return throughout the period, which is a simplification. In practice, investment returns vary each year. For long-term equity investments, many UK planners use a 5–7% nominal annual growth assumption before charges. Always deduct your platform and fund charges from the return rate to model a net figure. This tool does not account for tax, inflation, or changes in contribution levels over time.
Common mistakes
- Assuming a constant return without checking a more conservative growth rate.
- Forgetting ongoing contributions, fees or tax wrappers where relevant.
- Focusing only on the final balance instead of the path required to reach it.
- Ignoring the drag of charges over a long period.
What to do next
- Test a cautious, expected and optimistic growth rate.
- Compare this result with related savings or retirement tools before committing more money.
- Consider charges and any tax wrapper that applies.
- If the projected balance falls short, increase the contribution until the result meets your goal.