Texas case law I have read states that the blade will be measured from the handle, not the sharpened edge.
That's how every state does it AFAIK, if only word "blade" is used without other qualifying definition.
Rather logical to me, as everything before handle is what may be thrust into something. Think push dagger as perhaps most obvious example: those extra inches of non-sharpened area add lethality by increasing penetration.
The UK actually has a "cutting edge of its blade exceeds 3 inches" definition for its carry law. Never seen one like that here.
- OS