English is an alphabet, just an impure one. Each letter does have a consistent set of sound mappings.
First of all, separate letters from digraphs (letter combinations denoting one sound).
I’m not going to use IPA systems because I don’t know them, but just a basic phonetic script to show my point.
Consonant letters:
b = /b/
c = /k/ or /s/
d = /d/
f = /f/
g = /g/ or /j/
h = /h/ but is sometimes silent
j = /j/ except in Iberian loanwords
k = /k/
l = /l/
m = /m/
n = /n/
p = /p/
q = /kw/
r = /r/
s = /s/ or /z/
t = /t/
v = /v/
w = /w/
y = /y/ or /i:/
z = /z/
Consonant digraphs:
ch = /ch/
ci = /sh/
ph = /f/
sh = /sh/
ti = /sh/
th = /th/, but differentiated into two similar forms
Vowels:
a = /a/, /a:/, or the schwa
e = /e/, the schwa, or acts as a lengthening code for another vowel
i = /i/, /i:/, or /“eye”/
o = /o/ or /o:/
u = “hard /u/”, “soft /u/”, or /u:/
Vowel digraphs:
ae = /i:/ or /e:/
ai = /e:/
au = like in laud (except in “Saudi” and “mauve”)
ee = /i:/
ea = /i:/
ie = /i:/
oa = /o:/
oe = /o:/
oi = /oi/
ou = /ou/
oo = /u:/ or soft /u/
Vowel-consonant multigraphs:
all = like in ball
air = like in fair
ar = /a:/
are = like in fair
augh = /or/ or /a:f/
ay = /e:/ (except in “quay”)
ear = like in bear
ew = like in few
or = like in poor
ough = seven different sounds
oy = /oi/
ow = like in cow
Finally we have our special rule that in [vowel-consonant] the vowel is generally short (when the consonant isn’t r) and that in [vowel-consonant-e] the vowel is generally long.