Number crunchers from the University of NSW have analysed Melbourne Cup results during the past two decades and discovered a formula that would have given a better return than saving at a bank.

From an initial outlay of $4,896 on Melbourne Cup Day in 1989, this "winning formula" would have returned a profit of $40,885 by 2008 - a return of 154 per cent.

By contrast, you would have had to invest that figure in a savings account with a compound interest rate of 11.23 per cent 20 years ago, or, based on current rates, be prepared to wait until 2045.

The formula is called the Melbourne Cup Trifecta 50 or MCT50.

The bet eliminates all horses from the line-up that have odds longer than 50 to one, and puts $1 on all possible Box Trifecta combinations for the remaining starters.

"Like any strategy, this formula is not fool proof," said Anthony Dooley, head of the School of Mathematics and Statistics at UNSW.

"However, historically it seems to be every bit as safe as investing in the share market, and it certainly provided a greater return than traditional bank account investments."

The MCT50 does come with a warning.

This formula will have a one-in-three chance of actually returning a profit in any given year, and an individual would have had to stick it out for 20 years to reap the full rewards.

Professor Dooley also urges a strong note of caution for anyone considering this exact strategy next Tuesday.

"For the MCT50 approach to work in the future you would require a scenario which is statistically similar to the past - if everyone starts to use the same cut-off approach the odds worsen, and payouts fall dramatically," Prof Dooley said.

While racing experts normally keep their strategies to themselves, mathematicians see part of their role "to champion the patterns" that help explain and predict everyday activities.

"That includes the Australian light-hearted love for a bet," he said.

He also offered some worthy advice.

"If you really want to back a winner, invest in your own long-term learning, so that you can accumulate practical information that will help you inform your own daily decisions - both banking and betting."