Understanding SMS Character Limit and Segments

*Your Appointment Reminder subscription comes with a limit to how many reminders you can send each month.  You should keep your SMS segments to 1 if you only want to use 1 reminder per appointment.  Using multiple segments per SMS  will increase the number of reminders you will need each month.

A single SMS (text) message has a size limit. The standard limit is 160 characters. If you exceed this limit, the message will be split. Larger messages are broken into 153 character ‘segments’ and each segment is an additional charge and each segment affects your SMS quota. The reason for more than one segments size changing from 160 characters to 153 is there is some additional information that each segment must contain so the recipient can put the message back together correctly from the segments. For example if a message contains 165 characters, there will be two segments one of 153 characters and one of 12 characters.

Character Encoding

The original SMS standard defined a protocol (the 1985 GSM Protocol), which limited the characters that could be sent in a text message to 128 different characters, which was really only suitable for English, and a very limited set of special characters. Modern phones in addition to supporting messages up to 1600 characters also support a much larger character set, non-English characters, emoticons and emojis. If you include any of these non-GSM characters, those messages will be sent via a different encoding, the UCS-2 encoding. Messages that contain any UCS-2 (non-GSM) characters are limited to 70 characters with multi segment messages being 67 characters each. 

Smart Swap

In some cases, certain characters may sneak into messages that look remarkably like standard GSM characters but are not. Most notable are left (“) and right (”) quotes which can get into messages if copy and pasted from other apps, and certain characters, specifically whitepace characters are almost impossible to tell. In an attempt to keep the cost of messages down, Appointment Reminder will attempt to swap out these characters for a standard character equivalent. Should Appointment Reminder detect any of these characters in the message, an icon in the bottom right corner of the script will appear (smart swap icon), indicating that smart swap has or will be done.

Smart Swap characters

Character Description Replaced with
« Left-Pointing Double Angle Quotation Mark
» Right-Pointing Double Angle Quotation Mark
Left Double Quotation Mark
Right Double Quotation Mark
ʺ Modifier Letter Double Prime
ˮ Modifier Letter Double Apostrophe
Double High-reversed-9 Quotation Mark
Heavy Double Turned Comma Quotation Mark Ornament
Heavy Double Comma Quotation Mark Ornament
Reversed Double Prime Quotation Mark
Double Prime Quotation Mark
Left Single Quotation Mark
Right Single Quotation Mark
ʻ Modifier Letter Turned Comma
ˈ Modifier Letter Vertical Line
ʼ Modifier Letter Apostrophe
ʽ Modifier Letter Reversed Comma
ʹ Modifier Letter Prime
Single High-reversed-9 Quotation Mark
́ Acute Accent
ˊ Modifier Letter Acute Accent
` Grave Accent
ˋ Modifier Letter Grave Accent
Heavy Single Turned Comma Quotation Mark Ornament
Heavy Single Comma Quotation Mark Ornament
̓ ̓ Combining Comma Above
̔ ̔ Combining Reversed Comma Above
, Presentation Form For Vertical Comma
Presentation Form For Vertical Ideographic Comma
÷ Division Sign /
Big Solidus /
̷ Combining Short Solidus Overlay /
̸ Combining Long Solidus Overlay /
Fraction Slash /
Division Slash /
/ Fullwidth Solidus /
Big Reverse Solidus \
Reverse Solidus Operator \
  Combining Reverse Solidus Overlay \
\ Small Reverse Solidus \
\ Fullwidth Reverse Solidus \
̲ Combining Low Line _
_ Fullwidth Low Line _
Combining Long Vertical Line Overlay |
Combining Short Vertical Line Overlay |
Divides |
Fullwidth Vertical Line |
Left Vertical Box Line |
Right Vertical Box Line |
Vertical Line Extension |
Left Parenthesis Extension |
Right Parenthesis Extension |
Horizontal Scan Line-7 -
Horizontal Scan Line-9 -
Horizontal Bar -
- Small Hyphen-minus -
- Fullwidth Hyphen-minus -
Hyphen -
Hyphen Bullet -
ǃ Latin Letter Retroflex Click !
Single Low-9 Quotation Mark ,
̦ Combining Comma Below ,
, Small Comma ,
Small Ideographic Comma ,
, Fullwidth Comma ,
Halfwidth Ideographic Comma ,
Medium Left Parenthesis Ornament (
Medium Flattened Left Parenthesis Ornament (
Mathematical Left Flattened Parenthesis (
Left White Parenthesis (
Medium Right Parenthesis Ornament )
Medium Flattened Right Parenthesis Ornament )
Mathematical Right Flattened Parenthesis )
Right White Parenthesis )
Low Asterisk *
Asterisk Operator *
Circled Asterisk Operator *
Four Teardrop-spoked Asterisk *
Four Balloon-spoked Asterisk *
Heavy Four Balloon-spoked Asterisk *
Four Club-spoked Asterisk *
Heavy Asterisk *
Open Centre Asterisk *
Eight Spoked Asterisk *
Sixteen Pointed Asterisk *
Teardrop-spoked Asterisk *
Open Centre Teardrop-spoked Asterisk *
Heavy Teardrop-spoked Asterisk *
Heavy Teardrop-spoked Pinwheel Asterisk *
Balloon-spoked Asterisk *
Eight Teardrop-spoked Propeller Asterisk *
Heavy Eight Teardrop-spoked Propeller Asterisk *
Squared Asterisk *
˖ Modifier Letter Plus Sign +
Ideographic Full Stop .
Halfwidth Ideographic Full Stop .
ː Modifier Letter Triangular Colon :
Modifier Letter Colon :
˸ Modifier Letter Raised Colon :
Z Notation Type Colon :
Reversed Semicolon ;
͇ Combining Equals Sign Below =
Modifier Letter Short Equals Sign =
Latin Letter Small Capital A A
ʙ Latin Letter Small Capital B B
Latin Letter Small Capital C C
Latin Letter Small Capital D D
Latin Letter Small Capital E E
Latin Letter Small Capital F F
ɢ Latin Letter Small Capital G G
ʜ Latin Letter Small Capital H H
ɪ Latin Letter Small Capital I I
Latin Letter Small Capital J J
Latin Letter Small Capital K K
ʟ Latin Letter Small Capital L L
Latin Letter Small Capital M M
ɴ Latin Letter Small Capital N N
Latin Letter Small Capital O O
Latin Letter Small Capital P P
ʀ Latin Letter Small Capital R R
Latin Letter Small Capital S S
Latin Letter Small Capital T T
Latin Letter Small Capital U U
Latin Letter Small Capital V V
Latin Letter Small Capital W W
ʏ Latin Letter Small Capital Y Y
Latin Letter Small Capital Z Z
ˆ Modifier Letter Circumflex Accent ^
̂ Combining Circumflex Accent ^
Combining Double Circumflex Above ^
Medium Left Curly Bracket Ornament {
Medium Right Curly Bracket Ornament }
} Small Right Curly Bracket }
̃ Small Tilde ~
˷ Modifier Letter Low Tilde ~
̃ ̃ Combining Tilde ~
̰ Combining Tilde Below ~
̴ ̴ Combining Tilde Overlay ~
Tilde Operator ~
~ Fullwidth Tilde ~
̳ Double Low Line _
Em Dash -
En Dash -
Single Left-pointing Angle Quotation Mark <
Single Right-pointing Angle Quotation Mark >
Double Low Quotation Mark

The below are smart swap white space characters, Unicode character codes are included for reference, all are replaced with a single space

Character Unicode Description
  U+00A0 No-break Space
  U+2000 Whitespace: En Quad
U+2001 Whitespace: Em Quad
U+2002 Whitespace: En Space
U+2003 Whitespace: Em Space
U+2004 Whitespace: Three-per-em Space
U+2005 Whitespace: Four-per-em Space
U+2006 Whitespace: Six-per-em Space
U+2007 Whitespace: Figure Space
U+2008 Whitespace: Punctuation Space
U+2009 Whitespace: Thin Space
U+200A Whitespace: Hair Space
U+202F Narrow No-break Space
  U+205F Medium Mathematical Space
  U+3000 Ideograhpic Space
  U+008D Reverse Line Feed
  U+009F <control>
  U+0080 C1 Control Codes
  U+0090 Device Control String
  U+009B Control Sequence Introducer
  U+0010 Escape
  U+0009 Tab (7 Spaces Based On Print Statement In Python Interpreter)
  U+0000 Null
  U+0003 End Of Text
  U+0004 End Of Transmission
  U+0017 End Of Transmission Block
  U+0019 End Of Medium
  U+0011 Device Control One
  U+0012 Device Control Two
  U+0013 Device Control Three
  U+0014 Device Control Four
  U+2028 Whitespace: Line Separator
  U+2029 Whitespace: Paragraph Separator
U+2060 Word Joiner

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