Literacy is one of those things that's incredibly hard to measure, because for much of history it's often not been measured or, when it has in a medieval context, it's often used to refer specifically to the ability to read and write Latin. English literacy in pre-Conquest England, for example, is likely to have been much higher than it would have been in the twelfth or thirteenth century as English was no longer in use as an elite language. Asser's Vita Ælfredi, for example, states that Alfred required all of his ealdormen and their sons to be sufficiently literate and numerate to carry out the bureaucracy of their shires themselves, and it's likely that this obligation continued further down the organisational hierarchy and throughout the tenth and early eleventh centuries. Wills are a common document from the Anglo-Saxon period, and appear to have been used not just by the nobility, but also by freeman peasants to dispose of their own land. Ælfric's Colloquy also implies that lawyers were a fairly common profession. There is unlikely to have been a similar level of literacy in French among the English peasantry in the 1200s, say.

Estimates of literacy vary wildly: Cressy's Literacy and the Social Order: Reading and Writing in Tudor and Stuart England, for example, estimates that only 10% of men and 1% of women were literate in English in the 16th Century, while Thrupp’s The Merchant Class in Medieval London suggests that, at least in this class bracket, there was some 40% Latin literacy and 50% English literacy. There are a number of problems that derive from class; naturally the peasant classes wouldn't have had much if any access to formal education; and it's quite possible that many cases of rudimental or partial literacy would have been dismissed out of hand by elites who considered effective fluency the real benchmark for being 'literate'. During the 14th Century Peasant's Revolt, for example, there is significant evidence of peasant leaders not only considering themselves capable of self-governance, but also being able of specifically identifying individual charters and clauses they considered particularly unfair, as well as communicating with each other via written letters.