The standard SEO best practice for years to keep meta descriptions at around 156-165 characters maximum.
The reasoning behind this is that this optimization helps to avoid the truncation of the meta description in the SERPs and as a result, helps to avoid high bounce rates.
Late last year, Google announced a change to the SERPsnippets, taking them up to 300 characters, more than double the usual 150-165-character limits that are recommended.
Moz performed an in-depth study that determined that writing 300-character long meta descriptions should be observed as a new limit. Then, Google quickly changed back to the standard word count character limit.
What does the Length of Meta Description Mean for SEO?
Continue to experiment and assess results and make changes based on those findings.
Listen to what Google and their spokespersons have to say about what should and should not be implemented, but also do your own testing. Test what they say and test what they don’t say.
Find out exactly what works for your site.
What are the Characteristics of a Good Meta Description?
Based on the research I did on this topic, as well as my own experience, I came up with this list of elements you need to write a good meta description: