Example result based on the prefilled values.
Result
30,940.79
Continue your plan
Useful next calculations
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.
A realistic New Zealand planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Initial Deposit (£)
NZ$150,000
Monthly Contribution (£)
NZ$150,000
Annual Interest Rate (%)
5%
Years
10 years
After entering these figures, focus on result first and then rerun the tool with a more cautious assumption to understand the realistic range of outcomes rather than relying on a single estimate.
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
- !Using an assumption that is not supported by a current local quote, bill, statement or official source.
- !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- !Mixing monthly and annual inputs without converting them consistently.
- !Forgetting location-specific taxes, fees, eligibility rules or payroll deductions where they apply.
- !Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.
- Use the result to prepare better questions for a lender, provider, adviser or employer rather than treating it as a final answer.
Frequently asked
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