The minimum weight for the Doncaster Mile will be dropped to 50 kilograms, bringing Sydney's premier handicap into line with the Caulfield and Melbourne Cups.

Under a change to the rules introduced on Tuesday, the minimum will drop two kilograms, giving a spread of at least eight kilograms with the race carrying a minimum topweight of 58kg.

Australian Turf Club Executive general manager of racing Matt Rudolph said the rule change for this year's Doncaster, which is worth $3 million, would add a new element to the race on April 12.

"The Doncaster over the famous Randwick mile is a race that has defined champions for over 150 years - particularly those who give away weight and still triumph," Rudolph said.

Some of the most famous Doncasters in recent decades highlight the different weights carried by champion horses, including Super Impose in 1990 and 1991, when he carried 57kg and then 59.5kg, Sunline (58kg in 2002) and More Joyous (57.5kg in 2012).

At the other end of the scale have been lightweight winners such as Soho Square in 1992 with just 47.5kg, Grand Armee (51.5kg in 2003), and Racing To Win (2006) and Triple Honour (2008) who both had 51kg.