judging by

judging by (something)

Based on something; taking into account and considering something. Judging by his expression, I reckon the boss was as surprised as the rest of us by the news. It looks like the previous tenants didn't even know there was a lawnmower here, judging by the state of the front yard.
See also: by, judge
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

judging by something

 and judging from something
to make a decision or judgment based on something. Judging by the amount of food eaten, everyone must have been very hungry. Judging from the mess that's left, the party must have been a good one.
See also: by, judge
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
See also:
References in periodicals archive ?
Swanson's study confirms the trend toward judging by an increasingly younger group of educators.