The good news is that the majority of consonants in English only have one phoneme. The bad news is that consonants are sometimes silent.
Three consonants are unnecessary and are not used in phonetic spelling. These are C, Q and X.
C in English either represents an “S” sound or a “K”.
Q represents a “kw” sound that is more usefully represented by these letters. The “u” that customarily follows a Q is usually silent.
X in English is generally pronounced as a “Z”. When it is preceded by an “e” the sound is often “eks”. “Taxi” can be rendered phonetically as either “taksi” or “takzi”, depending on dialect.
G is a consonant that has two phonemes, being either a “g” sound or a “j”. It is also a silent letter in some words. Phonetically G is used for a hard “g” and “j” is used for “j” sounds.
J is a relatively young letter, dating back to the middle ages. In other words it was necessary to create a letter to represent a phoneme that was in common use. It is therefore a little surprising that “j” was a letter that Benjamin Franklin did not include in his phonetic alphabet. Instead he represented the sound with his letters representing “dsh”.
Another letter Franklin eliminated was “W”. While some nationalities have trouble with pronouncing “w” it is a distinct phoneme in English. Like “j” it is a relatively new letter that came into common use in the early middle ages. Franklin represented “hw”/ “wh” and “w” with letter combinations such as “hu” and “uu”.
Y is a distinct phoneme when at the start of a word or syllable. In English pronunciation “yog” is phonetically distinct from “jog”, for example.
When H is placed after another consonant it generally has a softening effect. Some of the exceptions to this constitute some of the most widely used consonant digraphs.
SH is used in words such as “shush”.
CH is often rendered as TSH in many phonetic systems. An argument can be made that in the initial position “ch” may have a softer sound, closer to “jh”. This gives us the words “jhurtsh” and “jhiyna” for “church” and “china”.
TH in English has two phonemes. It has an “f” sound in words such as “three” or “thigh”. This is rendered as “th” in many phonetic systems although “fh” may be closer in actual sound. TH words with a “d” or “v” like sound may be phonetically spelt with a “dh”. Many of the “dh” words are determiners or pronouns and include dhe, dhey, dhem, dhis, dhat, dhez, dhouz, dhayr and widh
PH is inherited from Greek and is phonetically represented by “f”.