Why is an SMS just 160 characters

The evolution of SMS

In the last few decades, the world has embraced an entirely new form of English. With less letters and more numbers than regular English, ‘SMS language’ or ‘Textese’ has taken the world by storm. But with such a high prevalence and common usage in our day to day communications, it can be easy to forget why textese words such as ‘TTYL’, ‘B4’ and ‘HRU’ are littered throughout our everyday mobile communications.

Related: The SMS turns 25 years old!

While advanced ‘message stitching’ technology makes it easy to forget about the strict 160 character limit on SMS messages, allowing our messages to become longer and less ridden with ‘text talk’, the limit still certainly exists. In the past, every message that exceeded 160 characters was sent as two entirely separate texts. Today, although it may appear that they are sent as one, every SMS that exceeds this limit counts as two.

But why 160 characters? Why any restriction on the number of characters in an SMS whatsoever? And where did this absurd rule come from? This question has long plagued the minds of ardent SMS senders, and we answered it back in 2015 but we thought it was time to shed some light on this again. While poor documentation and a fair few rumors has made finding the true origin of the 160 character limit a little bit messy, we’ve found the two most plausible answers. We’ll let you decide which one you think is true.

The first story centers around a gentleman named Friedhelm Hillebrand. Friedhelm was a chairman of the Global Systems for Mobile Communications (a group that sets standards for the Global Mobile Market) and as an important man, he was given an important job – to set the limit on the amount of characters a text message could contain.

Being the practical man he was, Friedhelm sat down with a typewriter and a cup of tea, and started jotting down some random sentences and questions. When he’d written a fair few, he counted the number of characters in each and found the average number of characters – around 160.

Next, he took a bunch of postcards that he had received, counted all the letters in every sentence and found that the average amount was just under 150. Lastly, he analyzed a number of the messages that came through on a Telex. Telex transmitters didn’t have a character limit, so you might expect that each message was around two to three hundred characters long. Well, in fact, Friedhelm found that on average, the character count was about the same as the messages received on the postcards. What a coincidence! Friedhelm took this research back to the board, and based on it, they decided to set the restriction that would make each SMS 160 characters.

The second story is a little more technical, and potentially a little more accurate. The organization that Friedhelm worked for, the Global System for Mobile Communications (GSM), had cellular towers all over the place that were used to interpret calls through a system called ‘packets’. These packets have limited space, and once the call information is taken out, we’re only left with (140 bytes).

When sent, SMS messages don’t get their own packets when they’re sent from tower to tower, they ride on the back of the call ones. So, it’s believed that Friedhelm and his colleagues had a look at this remaining space and made an educated guess as to how many SMS characters they could squeeze in there.

Back in 1985, one character pretty much equated to one byte, so they decided that the character limit for an SMS should be 140. Since then, the GSM technology has improved and they’ve been able to make each character less than one byte, meaning they could squeeze 160 characters into a message. Thus, the decision to limit each SMS to 160 characters.

Whether story one is accurate, or the truth is in story two, or, in fact, it is a combination of them both we may never know - but we sure do enjoy hearing the theories.

Which one do you believe?