The title has certain characteristics when used in a blog post or a web page. It has to be catchy to grab the attention of the user and explain in a few concise words what the rest of the article is about. Therefore, having a very good title has some SEO advantages:

• SERP (Search Engine Result Page) Display: It is the very first thing that the user sees about your article and plays the important part of enticing the reader to visit your page and read the rest of the content. This process thus allows you to improve the search Click-thru rate (CTR) for your webpage.
• Cumulative SEO Effect: As more users click on the link, it increases the CTR of the page and the search engine over time learns that your page content is relevant to the keyword and the search query. This will arguably improve your ranking within the SERP.

Google shows only about 70 characters in its search pages as the title. This can vary a little bit depending on the title and pixel size of the characters. Other search engines such as Bing and Yahoo also show roughly about the same character length. Also keep in mind that the displayed character length could change over time with every revamp of the search page layouts.

Also, consider that it is possible for another search engine or Google to show more than 70 characters on their pages in the future. Yahoo used to display 120 characters not so long ago.

It is unrealistic to imagine that you will go back and re-do all your title tags if something like that were to happen in the future. So the exact length is not as relevant and we will consider 70 characters as the average size that is displayed in SERPs.

The rest of the title over 70 characters is truncated using the ellipsis (…) or three dots to indicate that all of the title is not displayed. In a true technical sense, there is really no required length of the title. It can be as long or as short as you want.

We will try to decipher as to what an ideal length of a good title tag should be for SEO purposes. The title should not be very descriptive, that is what the description meta tag is supposed to be for. Some would argue that the length should be the same as the number of characters that is displayed in the search engine result pages (SERP), but this is not entirely accurate.

What is Not too short?: It should not be too short that it does not tell the user exactly what the content is about. Also, make it descriptive enough to fill out the space provided to you, otherwise it is a waste of space really. Do not make the titles too concise just to make it short, make sure that it reads as a complete sentence to the user. Write for the human reader rather than the search engine.

So, ideally let's say that your title tag should at least be 70 characters long.

What is Not too Long?: There is no reason to have extremely long titles. That should be part of the description tag. Having extremely long and redundant title can actually work against you in that it can be viewed as keyword stuffing. We are talking about long title tags upwards of 200 characters or more…

So, we can deduce that ideally your title tag could be anywhere between 70 to 200 characters. As mentioned earlier, when the title is more than 70 characters long, it is cut off in the search pages and not displayed. This however doesn't mean that the search engines do not read, index and take into consideration the entire title tag. The extra characters are still indexed and used to match queries both syntactically and semantically.

Google is taking into consideration the semantics (or the natural language meaning) of the query when displaying the results with each of its algorithm updates. This makes the need for a good semantically correct title even more important.

Start out by writing a title that correlates best with the content of the page, accurately describes the content and is a complete sentence and is eye catching without the consideration of length. After you have written this,  you can optimize it further if it falls into a category where it is either too small or too long.

If the title tag you have written is way less than 70 characters, then try to make it more descriptive to include more information to get it as close to 70 characters as possible. If the best written title is still below the "magic" number, do not fret too much about it and let it be.

When the title tag is above the 70 characters and is sure to be truncated, try to use it to your advantage. There are certain things that can be done to make the best of it.

• Primary Keywords: You should put the primary keywords that you want displayed towards the beginning of the title. The words that are earlier in the title is said to have more weight than the rest. It will also make sure that these keywords are emphasized and highlighted in the results, thus increasing your chances of catching the user's attention.
• Stop Words: You probably already understand the importance of word separators or stop words in the title tag. That means you should always use stop words as required to make the title a grammatically correct and readable sentence. Again write for the human reader. Skipping the stop words, even if it is not indexed by the search engine is not a good long term strategy.
• Legible Title: Make sure that the part of the tile that is displayed still makes complete sense when read by the user. You can then use the ellipsis as a "call for action". If you have written web ads, especially Adwords, then you know how to work this. Make the title intriguing enough so that the reader wants to know what the rest of the title (and thus the content) is.

Let us go through a couple of generic ideas for doing long titles:

• Try to make the last word before the truncation to be a stop word such as 'and', 'for', 'to' etc. Eg: Seven Tips for your phone, tablet, computer, home theater and …
• Another set of words that can be the last word is adjectives like 'best', 'biggest', 'largest' etc. Eg: Why the title is the most important factor affecting SEO and the biggest …

Now, As you can see there is really no ideal one-size-fits-all length for your title tag for your pages. It depends entirely on the content of the page and what you are trying to convey. But if I have to choose one, I would say keep it to anything between 70 and around 100 characters or so.