The formula
width ≈ characters × average width per character
Where it comes from
Google truncates by pixels, not by characters: around 580 for the title and 990 for the description. Since every letter takes a different width — an M is three times a lowercase L — counting characters is an approximation, convenient but imperfect. So both figures appear here: the characters, which you can count by eye, and an estimate of the width assuming an average character. A title in capitals or full of Ms gets cut sooner than the count suggests.
How to work it out by hand
- Count the characters in the title, spaces included
- Compare them against the limit of around 60
- Do the same with the description and its limit of around 155
- If you go over, the excess does not vanish: it is replaced by an ellipsis
What is worth knowing
Going over is not catastrophic and falling short is not either: Google rewrites the displayed title in a considerable share of searches, particularly when its own version matches the query better. What does matter is putting the essential part first, because that is the only part sure to be seen. And the meta description has not been a ranking factor for years: it affects how many people click, which is a different thing and also matters. One practical piece of advice: write the description as a concrete promise of what is on the page, not as a list of keywords. It shows, and it shows in the click.