“The end of November saw a spike in the average length of SERP snippets. Across 10K keywords (90K results), we found a definite increase but many oddities, such as video snippets. Our data suggests that many snippets are exceeding 300 characters, and going into 2018 we recommend a new meta description limit of 300 characters.”
“Unless something changes, and given the partial (although lacking in details) confirmation from Google, I think it’s safe to experiment with longer meta description tags. Looking at the clean distribution, and just to give it a nice even number, I think 300 characters is a pretty safe bet. Some snippets that length may get cut off, but the potential gain of getting in more information (when needed) offsets that relatively small risk.”
To read the full posting visit the MOZ page.