This all depends on what type of essay you were assigned to write. There are two different types of essays, particularly used in the IGCSE syllabus, and these include the "Critical Essay" and "Empathic Response." These two are the essays you're supposed to choose as your IGCSE portfolios towards the end of the year, or at least, that's what I was told in my school.
Critical Essay - 800-1200 words [Font Size 11 / 12 recommended, double spacing and Times New Roman FONT].
Empathic Response - 600-1000 words [Font Size 11 / 12 recommended, double spacing and Times New Roman FONT].