Simplicity managing director Sam Stubbs said the calculator was designed to make it easier for people to work out what they were paying.
"Because that is how everybody thinks about how they pay bills - power bills, water, rates - it is the one language everybody understands."
Stubbs said percentage figures made the amount sound low when it could be as much as 20 per cent of the return an investor was getting.
KiwiSaver members have paid out more than a billion dollars in fees to providers since the scheme was launched in 2007.
The dollar amount is growing every year because it is a percentage of the funds invested and balances are growing.
Stubbs said based on the average fee for KiwiSaver being 1.2 per cent the 2.7 million members were collectively paying about $480 million this year to have the $40 billion investment managed.
Stubbs said the calculator showed there were some huge differences in fees with the highest fee for a $30k balance being seven times more than the lowest fee.
"If this was a properly competitive market I don't think there would be a 6.5 to seven times price difference," he said.
Simplicity, which launched last year, has 6000 members and $160m in funds under management.