How many characters fit in one SMS?

The classic answer is 160 characters. That is correct, until you use one wrong character.

The ordinary alphabet

With the standard GSM alphabet, one message holds 160 characters. Send more and the message is split, after which each part holds only 153 characters, because room is needed to stitch the parts back together.

The expensive character

As soon as there is one character that is not in that alphabet — an emoji, an accent such as ë, a quotation mark your word processor converted — the whole message switches to Unicode. The limit then drops to 70 characters, and to 67 per part when split.

One emoji can therefore push a 160-character message from one to three messages, and triple your cost. That is the most common unpleasant surprise on an invoice.

What to do about it

Never copy straight from a word processor: it replaces straight quotes with curly ones. Count your characters up front, and watch personalised fields in particular — a name with an accent can make one in ten messages more expensive without you noticing.