Google displays roughly 600 pixels of meta title text on desktop, which translates to 50 to 60 characters depending on letter width. Titles longer than 60 characters get truncated with an ellipsis, which kills the closing hook. Titles shorter than 50 characters waste valuable real estate that could carry a benefit, brand name, or modifier.
The sweet spot is 55 to 60 characters. This is enough room to fit the target keyword, a benefit modifier (like Free, Best, Guide, Review), and the brand name separated by a pipe. Every variant this tool generates is locked to the 50 to 60 character range and shows you the exact count next to each title.