With these counters you can measure any text in pixels (as displayed by Google) or just count characters or words. The first counter will help you with SEO Titles (or metatitles). The second one can help you with metadescription (extract number should be set to 140-155 characters).
Words & Characters Counter
The title of a page that Google shows on its search results can sometimes be cut with an ellipsis because is too long. So how can you avoid this? What is that right length?
It is normally assumed that a Meta Title (this is the HTML <title> tag, the one that normally Google uses on the SERP), also known as SEO Title or HTML Title, shouldn't be longer than a certain number of characters, namely a maximum of 65-70 characters.
But this is wrong (or imprecise). Because Google doesn't limit a title based on its number of characters but rather on the number of pixel the title takes on the screen.
If Google search has a box of 600 pixels for titles in Desktop results, then obviously a title can never be longer than that. In fact, I would advise to make titles shorter than 570 px, which is, according to my own research, the maximum length before most of the titles get cut with the ellipsis. All of this is calculated with Arial font of 20px of size (the one used by Google on its page).
Mobile results can be longer (because titles can take more than one line), but using the desktop limit is safer as it's shorter. So your title will be displayed correctly in both Mobile and Desktop Google results.
Unfortunately, text editors such as Microsoft Word or Google Docs don't measure pixels and finding the right length could become a tricky exercise. But with this this SEO Title checker you can measure how long is your title in pixels.
When using the meter, don't forget the name of your site ("- mypage.com" or similar), as some CMS -like WordPress-, will add it automatically at the end and that will make the title longer. If the title goes beyond 570 px, the chances of showing a cut title are high and the tool will warn you with a red flag. Otherwise, a green flag means that the title will be displayed correctly on Google.