Example result based on the prefilled values.
| Result | Value |
|---|---|
| Result | 30,940.79 |
Continue your plan
Useful next calculations
Rates & 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 increasing your monthly contribution.
- When you want to compare best-case, base-case, and cautious return assumptions.
- When you need a quick projection before making a longer-term portfolio decision.
- When you are deciding how many more years of contributions are needed to reach a specific target balance.
- When you want to see whether starting earlier versus contributing more each month produces a bigger outcome.
Example: building a medium-term savings target
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
| Input | Value |
|---|---|
| Starting balance | £5,000 |
| Monthly contribution | £350 |
| Savings rate | 4.5% |
| Target period | 5 years |
The value of this example is seeing what comes from your own contributions versus the interest earned. That split is often what makes the next decision clearer.
How to read your results
Result
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator projects savings growth using compound interest applied to an opening balance plus regular monthly or annual contributions. The rate you enter should be the AER (Annual Equivalent Rate) advertised by your savings account, as this standardises for compounding frequency. You can model fixed-rate bonds, easy-access accounts, or regular savers by adjusting the rate and contribution fields.
The calculator assumes the interest rate remains constant throughout the term, which may not reflect reality — particularly for easy-access accounts, where rates can change with little notice. It does not model tax on interest income beyond your ISA wrapper or Personal Savings Allowance. For a conservative projection, consider entering a rate slightly below the current advertised rate to account for potential rate reductions. The tool does not include fees or account charges, which are uncommon for standard UK savings accounts but worth checking with your provider.
Common mistakes
- !Assuming a constant return without checking a more conservative growth rate.
- !Forgetting to include 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 platform fees or fund charges, which can reduce the real compounded return significantly over ten or more years.
- !Comparing ISA and general investment account projections without adjusting for the tax treatment of interest, dividends, or capital gains.
What to do next
- Test a cautious, expected, and optimistic growth rate instead of relying on a single projection.
- Compare this result with related savings or retirement tools before committing more money.
- Use the linked guides to understand which assumptions matter most over longer periods.
- Consider running the same figures in an ISA and a general account scenario to see how the tax treatment changes the outcome over ten or more years.
- If the projected balance falls short of your target, use the tool to work backwards — increase the monthly contribution until the result meets your goal.
Go deeper — 2 guides reference this calculator
- 7m
UK Mortgage Overpayments Guide: When to Clear Faster and When to Save Cash
How mortgage overpayments work, when they save the most interest, when early repayment charges matter, and when your cash should stay liquid instead.
- 6m
UK Emergency Fund Guide: How Much to Save, Where to Keep It, and What Comes Next
A practical emergency-fund guide covering target sizes, where to keep the money, how to build the buffer, and what to do once it is full.
Frequently asked
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