KiwiSaver investors are being urged to be aware of the assumptions made by online calculators when it comes to working out how much they will have in their savings pot at 65.

ASB Bank, New Zealand's second largest KiwiSaver provider, has become the latest to add a tool to its website to help Kiwis work out how much to save for their golden years.

But a quick check of providers who offer online calculators shows results can vary depending on what assumptions are built in including inflation, future pay rises and investment returns.

Paul Gregory, director of investor capability at KiwiSaver watchdog the Financial Markets Authority, said retirement income calculators could be a very powerful tool as they gave investors an interactive customisable way to see how choices they have made, or the ones they are considering, affect their ability to meet their goals.


"The FMA strongly agrees with the concept of retirement calculators. We link to the Commission for Financial Capability's calculator in many places on our website."

But he said savers should also be aware of the assumptions used by the calculators and consider how it would influence the calculator's result.

"The results of the calculators depend on how each provider has set them up. In particular, the assumptions about what the returns from various investments (like equities and property) will be, looking ahead.

"Some use the forecast returns of different types of funds. A balanced fund calculator will produce different results from a conservative one."

Gregory said investors should see the calculators as a trigger to have a conversation with their provider about whether their existing - or intended - investment was appropriate.

Online calculators have been controversial in Australia where the superannuation industry is much more established.

In 2005 its regulator bought in rules for calculators to stop superannuation providers from using them as a marketing tool to try and attract new members.

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More recently there have been accusations in Australia that some providers are not following the rules and their calculators are misleading people.

Gregory said there were no rules for how calculators should be set up in New Zealand but the fair-dealing provisions in the FMA Act enabled the regulator to intervene when information - including forecast information - was misleading.

"In this case it's just that the calculators are not standardised."

The Herald's research showed a $20k difference in the highest result from a KiwiSaver provider compared to government-backed money education website sorted.

David Boyle, head of investor education at the Commission for Financial Capability, which runs the sorted website said its calculators tended to be on the conservative side.

"At the end of the day we are here to give people a guide.

"It is better to be a little bit more considered rather than taking a true market outcome," he said.