The chain said on its Australian Facebook page there is no guarantee each footlong sub would measure 12 inches.
"Subway Footlong is a registered trademark as a descriptive name for the sub sold in Subway Restaurants and not intended to be a measurement of length," the statement said.
ABC News said a tempest started brewing when an Australian teenager went online to state he had measured a sandwich he had purchased at Subway and found it to be 11 inches in length.
The revelation led the New York Post to confirm not-quite foot-longs were being sold in the Big Apple.
Subway told ABC it strives for a 12-inch bun but the vagaries of commercial baking make it difficult to guarantee the results 100 percent of the time.