The following applies to 7-bit text messages:

The allowed character set is given below. You do not have to transliterate any characters to the GSM characterset: this is done automatically for you as far as possible. All characters given in the GSM 03.38 specification are supported.

For background, see this Wikipedia.org article. Note that under certain circumstances, characters not included in this list can be sent as 16-bit Unicode, instead.

Any characters that you submit which do not fall within this set, will be replaced by a full stop or question mark. Your submission will not fail.

Character	ASCII value	Hex value
[newline]	10	0A
[carriage return]	13	0D
[space]	32	20
!	33	21
"	34	22
#	35	23
$	36	24
%	37	25
&	38	26
'	39	27
(	40	28
)	41	29
*	42	2A
+	43	2B
,	44	2C
-	45	2D
.	46	2E
/	47	2F
0	48	30
1	49	31
2	50	32
3	51	33
4	52	34
5	53	35
6	54	36
7	55	37
8	56	38
9	57	39
:	58	3A
;	59	3B
<	60	3C
=	61	3D
>	62	3E
?	63	3F
@	64	40
A	65	41
B	66	42
C	67	43
D	68	44
E	69	45
F	70	46
G	71	47
H	72	48
I	73	49
J	74	4A
K	75	4B
L	76	4C
M	77	4D
N	78	4E
O	79	4F
P	80	50
Q	81	51
R	82	52
S	83	53
T	84	54
U	85	55
V	86	56
W	87	57
X	88	58
Y	89	59
Z	90	5A
_	95	5F
a	97	61
b	98	62
c	99	63
d	100	64
e	101	65
f	102	66
g	103	67
h	104	68
i	105	69
j	106	6A
k	107	6B
l	108	6C
m	109	6D
n	110	6E
o	111	6F
p	112	70
q	113	71
r	114	72
s	115	73
t	116	74
u	117	75
v	118	76
w	119	77
x	120	78
y	121	79
z	122	7A
¡	161	A1
£	163	A3
¤	164	A4
¥	165	A5
§	167	A7
¿	191	BF
Ä	196	C4
Å	197	C5
Æ	198	C6
Ç	199	C7
É	201	C9
Ñ	209	D1
Ö	214	D6
Ø	216	D8
Ü	220	DC
ß	223	DF
à	224	E0
ä	228	E4
å	229	E5
æ	230	E6
è	232	E8
é	233	E9
ì	236	EC
ñ	241	F1
ò	242	F2
ö	246	F6
ø	248	F8
ù	249	F9
ü	252	FC

Greek characters are mapped onto extended ASCII characters which are unused in the GSM character set:

Greek characters
Character	Equivalent	ASCII value	Hex value
Δ (delta)	Ð	208	D0
Φ (phi)	Þ	222	DE
Γ (gamma)	¬	172	AC
Λ (lambda)	Â	194	C2
Ω (omega)	Û	219	DB
Π (pi)	º	186	BA
Ψ (psi)	Ý	221	DD
Σ (sigma)	Ê	202	CA
Θ (theta)	Ô	212	D4
Ξ (xi)	±	177	B1

Example of a message body containing the Greek character gamma (decimal 172 == hex 0xAC):
This+is+a+gamma+%AC

Extended GSM characters are only supported on certain networks - please test before sending large volumes. Submit the (ASCII 187) character, followed by one of the following:

Character	Equivalent	ASCII value	Hex value
form feed	newline	10	0A
^ (circumflex accent/caret)	dc4	20	14
{	(	40	28
}	)	41	29
\	/	47	2F
[	<	60	3C
~	=	61	3D
]	>	62	3E
|	@	64	40
Euro sign	€	101	65