Level 50 is the highest level attainable in the game. Experience points max out at 999999.

Level Experience Required 1 0 2 40 3 196 4 547 5 1171 6 2146 7 3550 8 5461 9 7957 10 11116 11 15016 12 19735 13 25351 14 31942 15 39586 16 48361 17 58345 18 69617 19 82253 20 96332 21 111932 22 129131 23 148008 24 168639 25 191103 26 215479 27 241843 28 270275 29 300851 30 333651 31 366450 32 399250 33 432049 34 464849 35 497648 36 530448 37 563247 38 596047 39 608846 40 661646 41 694445 42 727245 43 760044 44 792844 45 825643 46 858443 47 891242 48 924042 49 956841 50 989641

Courtesy of Final Fantasy Classics.