Beefier is better. Or at least that is McDonald's bet as it tries to increase burger sales. (Tweet this) The chain is coming out with a bigger quarter-pounder patty that will weigh 4.25 ounces before cooking and have a new shape, making it more of a quarter-pounder plus, according to an internal document reviewed by CNBC.

McDonald's current quarter pounder with cheese hamburger whose patty is 4 ounces before cooking. McDonald's

The current patty stands at 4 ounces before cooking and shrinks to 2.8 ounces after cooking, according to McDonald's Twitter account. The chain also detailed new assembly procedures for the burger to make the searing more visible.

The new patties will roll out within the next month, according to one franchisee director of operations. McDonald's declined to elaborate on the expanding burger.

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"As (CEO) Steve Easterbrook has shared, we're always innovating around McDonald's food, drinks and restaurant experience based on customers' preferences, and that includes hotter food and reviewing cooking procedures, and we'll share more details soon," the company said in a statement.