The highest IELTS Band required is 7.5, by the Research Centre for English and Applied Linguistics at the University of Cambridge . Minimum IELTS score required depends on various factors like: program you choose, university you choose, level you want to join etc. However at an average university in UK, for undergraduate arts subject, IELTS band score of 6.0 will be sufficient (for some even 5.5 band score will do). However for post graduate level minimum IELTS band score requirement is 6.5 for most of the universities.
Most IELTS requirements by universities fall between 5.5 and 7.0. For example:
University Minimum IELTS score
Liverpool University 7.5
Cambridge University 7.0
Birmingham University 6.0
Essex University 5.5
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