as fast as your legs can carry you
as fast as (one's) legs can carry (one)
As fast as one can run away. You need to get away from here as fast as your legs can carry you—it's too dangerous!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
as fast as your legs can ˈcarry youas quickly as you can: When he heard the police sirens, he ran off as fast as his legs could carry him.
Farlex Partner Idioms Dictionary © Farlex 2017