The definition of a legal knife blade can be different from state to state. For instance. the state of Texas said in an unpublished appeal (Perez v. State 1999 WL 521705) that a knife blade includes the sharpened and unsharpened parts of the blade above the knife handle. The American Knife and Tool Institute states that a knife blade should be measured from where the knife handle ends. Follow the steps below and check state laws to find out if your knife may be carried legally.
Place the knife on a table with the blade out.
Place the end of the measuring tape or ruler against where the blade meets the knife handle at the lowest intersection.
Measure blade to its highest point at tip. This is your blade measurement.