Meta description length, measured the way Google actually cuts it.

There is no character limit, because Google does not truncate by characters. It truncates by pixel width, and a description of capital Ws is far wider than the same number of lowercase Is. Character counts are a proxy that happens to work most of the time and fails on exactly the descriptions people worry about.

As a working figure, a desktop snippet gives you roughly two lines and a mobile one roughly three, which lands most descriptions between 120 and 160 characters. This tool measures the actual width instead, so you can see where your specific sentence cuts rather than guessing from an average.

Not directly. Google has been explicit that it is not a ranking factor, and it has not been one for many years. What it affects is whether somebody clicks, which affects everything downstream.

So it is worth writing well and not worth agonising over. A description that gets cut mid sentence looks careless. A description three characters over an arbitrary limit does not matter at all.

Because it frequently decides a passage from your page answers the query better. Independent studies have repeatedly found Google rewriting the majority of descriptions, and in practice most sites see their written description used less than half the time.

That is worth knowing before you spend a morning on this. The description is a suggestion, not a setting. It gets used most often on branded and navigational queries, and overridden most often on long tail ones where a specific passage in the body is a better answer.

It is an approximation and we would rather say so than imply precision we do not have. The measurement is taken in your browser with the same technique Google's own layout uses, but the exact font, size and container width vary by device, by locale, by whether a date or a favicon is shown, and Google changes them without announcement.

Treat the boundary as a guide with a margin either side, not a hard line. If your description sits within a few pixels of the cut, assume it may cut.

Every page that matters, yes. Duplicated descriptions across a large template are a signal that the pages are near duplicates, which is a bigger problem than the description itself.

For very large sites, generating them from real page data beats writing thousands by hand or leaving them empty. An empty description is not a fault, though. Google will construct one from the page, and on a long tail page it frequently does a better job than a generic hand written line.