It's a bit of a misconception in regards to titles and meta descriptions using character lengths. Google now use pixel width for titles and meta descriptions in the results pages like other search engines.
Titles are around 480 pixels and you have around 920 pixels to play with in regards to meta descriptions (for desktop results). You have to take into account bolding of keywords, too. You can use the free version of the Screaming Frog SEO Spider Tool to simulate this in their SERP snippet tool, or use one of the many free online tools. I use the paid version, as it's invaluable in my work doing SEO and audits for clients.
Please note: these are still only estimated.
In regards to what they are, and what i would use as best practices:
(Copied and pasted from one of my audits!)
Titles:
The Title tag is the first description of the page that search engine users will read, and it is extremely important to both users and search engines that it contain the keyword, or key phrase that they are searching for. This will not only help to improve rankings, but can significantly improve your click-through-rate as well.
A proper Title Tag will:
- Be unique to that page (do not use the same Title Tag on multiple pages).
- Use the keyword or key phrase of that page twice if space permits (once at the start, followed by a separator such as a colon, hyphen or pipe. It should also then be used once again in a call to action). If the size limit prevents the use of the keyword twice, use it once in a good call to action, with the keyword as close to the beginning of the Title Tag as possible.
- If relevant, include a geo-qualifier (such as a town, city, county or country).
I'd use a format such as:
Home Page: Primary and Secondary Keywords or Tag Line | Company Name
Other Pages: Primary and Secondary Keywords | Company Name
Meta Descriptions:
Meta Descriptions, while not as important for search engine rankings anymore, are extremely important in gaining user click-through from search engines. These are short paragraphs and provide you with an opportunity to advertise your content to searchers and let them know that you have exactly what they’re looking for. The Meta Description should employ the targeted keywords and key phrases intelligently in order to create a compelling description that a searcher will want to click. Direct relevance to the page and uniqueness between each page’s Meta Description is key.
The following list is the guidelines for Meta Descriptions and how they should be formatted to increase click-through-rate for search engine users:
- Be unique and relevant to that page.
- Be descriptive and contain a call to action.
- Contain 1 – 2 complete sentences with correct punctuation, and no more than 5 commas.
- Use the keyword or key phrase once per sentence, as close to the start of each sentence as possible.
- If relevant, include a geo-qualifier (such as a town, city, county or country).
Hope all of this helps.
