The enlisted grades correspond with the NATO rank codes, with E-1 being equivalent to OR-1, E-2 equivalent to OR-2, and so on.
ðɪ ɛnlˈɪstᵻd ɡɹˈeɪdz kˌɔːɹɪspˈɑːnd wɪððə nˈeɪɾoʊ ɹˈæŋk kˈoʊdz, wɪð ˈiː wˈʌn bˌiːɪŋ ɪkwˈɪvələnt tʊ ɔːɹ wˈʌn, ˈiː tˈuː ɪkwˈɪvələnt tʊ ɔːɹ tˈuː, ænd sˌoʊ ˈɔn.