This measures a batch of title tags against the width search results typically display, flagging those that will be cut off.
The working limit
Around 60 characters on desktop, though the real constraint is pixel width rather than character count. Titles beyond that truncate with an ellipsis.
Both extremes cost you
Too long and the end of the message disappears — often the part carrying the differentiator. Too short and you have left space unused that could have earned the click.
What to do with the flagged set
Front-load. Move the distinguishing words to the start so that whatever survives truncation is the part that matters.
Try it: Meta Title Length Checker on SeoWolf's Notepad.