Different freelance writers and companies have their own standards as to how many words mean 1 page to them. However, one thing remains the same across all the writers and companies: they charge on the basis of words divided by the total number of words that they believe makes up for 1 page, i.e. 1100 words / 275 words = 4 pages.
Most frequently, I have come across 275 words as one page or 300 words as one page offered by different companies and writers. Yet, a majority have the 275-word length as the standard one page.
Double-spaced, Times New Roman or Ariel type faces, 1" margin on all four sides of the sheet, are usually the requirements from most of the institutions. So, these have also been added to the standard page length norms.
So, I think most of us might mean one page as: 275 words, Times New Roman, double-spaced, 1" margin on all four sides. I also follow the same word length as one page.