Large supermarkets will be required to display and advertise the unit price of all packaged grocery items by the end of this year.
Small supermarkets and corner stores have been exempted from the federal government plan, which is aimed at giving consumers more information about grocery prices.
Details of the mandatory national unit-pricing regime, released on Thursday, have been welcomed by consumer groups and retailers.
Unit pricing will apply to all store-based retailers that have a grocery display area greater than 1,000 square metres and supply a prescribed range of food-based grocery items.
More than half of Australia's supermarkets will thus need to comply with the scheme.
Online retailers that supply a prescribed range of food-based grocery items will have the same obligations.
Supermarkets will be required to include unit pricing on print advertising and website advertisements, but not broadcast advertising.
This means stores will have to display prices per unit measure - per 100 grams, 100 millilitres, per metre or per item.
''Unit pricing will help consumers compare packaged grocery items of different sizes easily and quickly,'' Consumer Affairs Minister Chris Bowen told reporters.
The system will be useful where the sizes of packaged items are similar but not identical, he said.
Some goods, such as meat or bread discounted at the end of the day, will be exempted from the scheme.
The low cost of the scheme pleases retailers.
''We have always supported a cost-effective national scheme and the government's model reflects this,'' Australian National Retailers Association CEO Margy Osmond said.
It was a better approach than prescriptive or state-based schemes that would cost more but give consumers no more useful information, she said.
Consumer advocate group Choice has hailed it as a win for consumers, though it still has some concerns about the scheme.
It wants supermarkets to display unit prices at a ''prominent'' size and wants the scheme to stipulate a minimum font size.
Choice also wants unit pricing applied to ''specials'' and ''multi-buys'', items exempted from the planned scheme.
Supermarket giant Woolworths plans to have its own unit-pricing program for about 19,000 products rolled out to all its 790 stores by September.
It says customer feedback since the rollout began in November has been very positive and the planned national scheme will involve little additional cost to retailers.
Discount supermarket ALDI - the first retailer to introduce unit pricing in November 2007 - says the planned scheme will provide a level playing field for Australian retail competition.
The Australian Competition and Consumer Commission, which recommended a unit-pricing scheme in its inquiry into grocery prices last year, will enforce the scheme.
The final version of the code comes into force from December.
AAP
