While a general guideline is one page is 500 words (single spaced) or 250 words (double spaced), this is a ballpark figure.

As a general guideline, it is recommended to have atleast 500 words of content on a page to give it some ranking potential. However this should be considered on a case by case basis. It may not be relevant for particular pages like 'contact us' pages for example.

To get to that point, however, your content should be at least 1000 words and no more than 2000. It's difficult to say exactly because Google changes its parameters often, but between 1000 and 2000 words seems to be their sweet spot.