Sheena, this depends entirely on your universities regulations! You need to obtaina copy of (if you haven't already) your universities regulations for PhD/MPhil degrees where the limit will be stated. At my uni, for instance, PhD is between 80-100k, and MPhil is between 60-80k. At another university (where a friend of mine is doing his PhD) however, the PhD is 60-80k and the Mphil is 40-50k. Also, university regulations usually state different word limits for different disciplines - e.g. arts, engineering and sciences have shorter words limits (for obvious reasons) than humanities and social sciences. So you really need to check your university regulations and if it's too vague (e.g. it says 'approx. 80k') then you need to double check with your supervisor. People on this forum can't help you since we are all doing different disciplines at different uni's.