As Roger and Allen have correctly noted, the maximum limit is 255; however,
you probably can't, nor should, have anywhere near that many.
There's another limit to contend with and that's 2000 characters per record
(excluding Memo, OLE and Attachments). That's only about 8 characters per
field on average.
Also properly normalized data seldom requires over 30 fields per table. The
data may need multiple tables though which are linked to each other.