how many pages is a phd thesis

Word limits
A PhD thesis should not exceed a total of 100,000 words in length (or 70,000 for most professional doctorates), including scholarly apparatus such as footnotes or endnotes, essential appendices and bibliography. A doctoral thesis should however, be concise. Examiners often criticise excessive length, which frequently indicates poor judgement.

References:

http://www.umass.edu/honors/curriculum/thesis