Australia's favourite beer is about to become lighter.

The alcohol content of Victoria Bitter will be cut by 0.2 percentage points to 4.6 per cent next month.

The price will stay the same, but the reduced alcohol content could save brewer Foster's tens of millions of dollars a year in beer tax.

VB spokesman Paul Donaldson said it was the only way the brewery could avoid raising the price.

"This is all about making VB better value so that when every other beer goes up in price this August, VB won't be," he said.

The change will come into effect on August 1 and applies to all full-strength VB products including stubbies, cans, long necks and on tap.