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Savings Calculator

Calculate how your savings will grow with regular deposits and compound interest. Enter your balance, monthly contribution and rate to project future savings.

Last reviewed 15 August 2026

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Calculator inputs

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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 realistic New Zealand planning example

Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.

A realistic New Zealand planning example
InputValue
Initial Deposit (NZ$)NZ$150,000
Monthly Contribution (NZ$)NZ$150,000
Annual Interest Rate (%)5%
Years10 years

After entering these figures, focus on result first and then rerun the tool with a more cautious assumption.

How to read your results

Result

The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.

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.
  • !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.

Frequently asked

Compound interest means you earn interest on both your deposits and previously earned interest. Over many years, this snowball effect can significantly increase your total savings beyond your contributions alone.

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