If you're counting sounds (i.e. phones), then most languages with those same 5 vowel letters have quite a lot because of numerous allophones. English is crimin

If you're counting sounds (i.e. phones), then most languages with those same 5 vowel letters have quite a lot because of numerous allophones. English is criminal in that it has many vowel phonemes - British more so than American - and then on top of that its mapping of them to vowel letters is completely out of whack with both traditional Latin values of them, and how they're used in most other languages out there. I mean, cmon, <ea> for /i:/? Still, with a sensible orthography, General American would only need something like 9-10 distinct vowel characters (for monophthongs; but diphthongs are best spelled as the obvious corresponding vowel-vowel or vowel-semivowel sequences anyway).