How literate were common people in Medieval Europe?

There is an interesting publication, "Literacy and Education in England 1640-1900" by Lawrence Stone in 1969. (If SciHub suits you, you can search there for that internet address.) It focuses on England, but also glances elsewhere in Western Europe. It does not stray back into the medieval period, which may be the main focus of the question, but it may give some insights for that period (and the question itself seems interested in later centuries as well). Here are some snippets from that paper:

The Protestation Returns of 1642 2 gave an almost complete survey of adult males, with signatures or marks. (There is discussion about how well literacy can be judged by the ability to write your own name, and the hope is that the connection is not bad. Remember that people are writing their names many years after they left school.) "One may tentatively conclude that the average male literacy rate on the eve of the Civil War was probably not less than 30 per cent, varying from 15 to 20 per cent in the rural north and west to up to 40 per cent in the countryside near London; and that the rate in some of the larger towns of the south was as high as 60 per cent."

Some breakdown between classes is attempted. For marriage records in Oxfordshire and Gloucestershire, there is very little change for the "labouring and servant" class from 1675 to 1800: literacy stays around 45% (except for a sharp dip around 1775, probably due to population growth). Meanwhile, the "yeomen/husbandmen" class rose from 55% to 90%. In that class, the marriage records go back to 1625, and there was a large but inexplicable disparity between the two neighbouring counties: 68% literacy in Glos. versus <40% in Oxon. However, these marriage records correspond to an expensive way to get married, and "the bottom half of the population is barely represented in this sample". (An amusing side comment: "It cannot be argued that the licensing system was favoured by couples in cases where the bride was already pregnant and therefore in a hurry, since it looks as if at least one third and possibly up to a half of all brides were in this condition anyway in the eighteenth century.")

One theme in the paper is that advances in literacy were often pushed by religious groups and in particular by religious rivalry. England's literacy may have benefitted from Protestantism, with its encouragement of Bible study. Scotland did even better with Presbyterians in charge of education. "Some puritan sects became 100 per cent literate at a very early stage: in post-1754 Quaker marriage registers, there is not a single mark to be seen, by either bridegroom or bride." School policy and funding are responsible for the eventual rises. The flipside of this is that without organised, funded and obligatory schooling, the natural rate of self-taught literacy was low. The other big opponent to child literacy was pressure to start work. Sometimes the ruling classes deliberately avoided teaching the lower classes literacy, to avoid heresy, discontent and revolution. These factors combine in some records for Beziers-Narbonne in France, 1575-1593: unskilled rural workers signed their names only 3% of the time (though another 7% wrote their initials). At around the same time, artisans in Montpellier were signing 63% of the time (plus 11% initialling).

There are some hints that literacy pre-Reformation and pre-printing was not common at all: "The parish priests of late medieval England were often illiterate. [...] Between a quarter and a third of the parish clergy owned at least one or two service books. [...] Of 311 clergy of the diocese of Gloucester in 1551, 168 were unable to repeat the Ten Commandments."

One last foray towards the medieval period: "In the Middle Ages literacy carried with it no special sense of status, since many of the highest nobles in the land could neither read nor write. In northern Europe, the end of this phase came in the mid-sixteenth century: the first earl of Rutland in England and the Constable Montmorency in France were the last illiterates to hold high office in their respective countries."

The Light Ages by Seb Falk writes, “Literacy was not as rare in medieval England as is often assumed — around half the population had a basic level, sufficient to read a familiar prayer” (pg. 30). (This is a book written for a popular audience, but written by a proper historian.)

I will also register a different opinion from Moishe as to the correlation of the ability to read and the ability to write. I read several languages fluently that I cannot write in the least, and I read one language where learning to write was very clearly a distinct skill. (It's harder to come up with the spelling of a word than to recognize it. Letter formation in a distinct skill. etc.)

Other answers are mostly about England. The Middle Ages were very long with several different stages. Europe is also huge.

While in the Early Middle Ages the Carolingian renaissance already flourished in one part of Europe, among Slavs virtually no-one could read or write, except for a handful of mainly Iro-scot missionaries. Mind you, this is not just "somewhere in Russia", but also in the regions that include today's Berlin or today's Hungary. Even in the West (Franconia), literacy was limited to the members of the church.

Later in the Middle Ages traces of surprisingly high literacy were discovered in some areas. A very notable example are the birch bark manuscripts of Veliky Novgorod. They were only discovered in the 1950s and were extremely surprising. They show that even ordinary people used birch bark to log notes or to deliver simple ordinary messages from someone to someone. Of course, velum or paper and ink were way too expensive for such purposes for ordinary people. The local environment is favourable for preserving these artefacts. We do not know to which extent this may or may not have extended to wider areas. The existence of Church Slavic, similar enough to the local East Slavic vernacular, as a literally language have certainly helped.

It is perhaps also right to mention the Hussite movement in the 1420s and 1430s. It all began even earlier when Bibles translated to vernacular (Old Czech editions) became common enough and individual non-church-appointed preachers appeared travelling in the country and interpreting it. This were still mostly people with university (there was one in Prague since 1348) or other higher education and the Bibles were still relatively expensive manuscripts.

There are many historiographical works that have dealt with this problem. Most are currently unreachable to me, but I will give a link to an overview of such literature:

Mostert, M. (1999). A bibliography of works on medieval communication. In New Approaches to Medieval Communication (pp. 193-318) https://doi.org/10.1484/M.USML-EB.3.4838

it is really just a long list (1580 titles) of bibliography, but many of those cited works should be about this very topic. It obviously does not contain any new research from the 21st century.

In the introduction of one of the quoted works: Bäuml (1980) Varieties and consequences of medieval literacy and illiteracy the author repeats that the medieval literacy was mostly the Latin one (implicitly limiting themselves - at least in the introduction - to the West and to the earlier periods before vernacular literatures in the late Middle ages) and also mentions one of the arguments that was repeated here, that the ability to read and the ability to write are not necessarily dependent on each other.

The same author in Scribe et Impera: Literacy in Medieval Germany (1997) shows how the literacy and the Latin language vs. the vernacular language influenced different layers of the society and led to "heresies" such as the Hussite movement in Bohemia that I mentioned above:

... The gradual spread of vernacular writtenness, gathering speed in the twelfth Century and becoming a flood with the inven- tion of printing ... . The translations of Christian texts from Latin into the vernacular during the Carolingian era served to establish the power of the Church on German territory. The layman was involved in these vernacular literarifications merely as listener to readings and observer of liturgical performances. There was no question of his having any direct access to writtenness - he had no need for it, unless it be as a member of the governing religious or secular establishment. During the Ottonian period, when the Christianization of what had become the Holy Roman Empire had been largely achieved, very little was produced in vernacular writing, if its transmission is any guide. With the twelfth Century, however, and in concert with the increasing rationalization of territorial governance, there began an increase in vernacular writtenness. Access of the laity to the written word, and particularly to religious texts, therefore also increased. This threatened the clerical monopoly of written knowledge, including its monopoly of the written Word of God, at the same time as it strengthened the laity’s selfconfidence in the face of that monopoly. Students and professors, attracted to the growing universities founded by lay powers to provide them with secular and religious knowledge, found that it was in their interest to Support the clerical monopoly of knowledge. In the later Middle Ages, in the fifteenth Century, municipal schools teaching writing (in German) and bookkeeping were founded as the necessity for literacy in business law, in business management and in business generally increased. Monastic and religious reformers of every stripe demanded more books and better access to books, and mystics of every stripe produced a steady stream of written material in the vernacular. And the Church soon saw heretics lurking in every corner.

All the above is about free people. People from the cities like merchants (or their children), free people owning a few villages and so on. Or even poor but free people like those travelling preachers. There is little hope in assuming that the non-free peasants (serfs) had the opportunity to learn to read or write anything. And if, then not in significant numbers.

Here are some semi-random quotes. I do not have time to chase the references, but they are coming from a modern professional historian, not from a You-tube personality, so I'd take his numbers seriously.

Robert A. Houston, "The Growth of Literacy in Western Europe from 1500 to 1800".

Houston is a professor of History at St.Andrews and wrote a book on the subject:

"Literacy in Early Modern Europe: Culture and Education, 1500–1800," London 2001.

Literacy is a relative concept that has meaning only in specific economic and social contexts, but historians tend to rely on universal, standard and direct indicators such as the ability to sign one’s name on a document. Using this measure it is clear that there were social distinctions in the ability to use a writing instrument throughout the early modern period.

At the end of the Middle Ages, the ability to write was restricted to less than 10% of men and hardly any women possessed it.

The change in literacy rates was halting and irregular. Judged by signing, the most pronounced early expansion occurred among the middle and upper classes, among men and in towns. In northern England the illiteracy of the gentry fell from about 30% in 1530 to almost nil in 1600, but that of day labourers stayed well above 90%.

You can find more numbers in his article (in particular, numbers in relation to different areas of Western and Central Europe). Yes, the ability to read is different from the ability to write, but in Houston's statistics he focuses on the ability to just write own name, which is the bare minimum of literacy and (IMHO) probably was highly correlated with the ability to read (at least in some language, be this Latin or vernacular).

Edit 1. Regarding Mark Olson's request, below are estimates of literacy at the end of the medieval times/early modern times from other authors.

All the books that I found which deal with numerical estimates of literacy in late medieval and early modern times favor the ability to sign as an estimator of the degree of literacy. In addition to Houston's book (whose book has the entire chapter comparing different methods, including ones which I find rather exotic, such as materials of Spanish Inquisition trials):

D. Cressy, Literacy and the Social Order. Cambridge University Press, 1980.

R. O'Day, Education and Society, 1500-1800: The Social Foundations of Education in Early Modern Britain. Longman, 1982.

Adam Fox, "Oral and Literate Culture in England, 1500–1700." Oxford University Press, 2000.

Cressy is especially thorough with providing numerical data and its statistical analysis.

Day compares for instance the analysis of literacy in Northern England in

Jo Ann Hoeppner Moran. "Literacy and Education in Northern England, 1350-1530: A Methodological Inquiry." Northern History, 17 (1981): 1-23.

based on estimates of the number of parochial schools and argues that Cressy's methodology is provides more reliable estimates.

On page 20 of her book O'Day says that Moran's numbers indicate that 15% of the total population of York diocese had undergone basic schooling by 1530, while Cressy indicates 10%.

O'Day characterizes as "wildly optimistic" the estimates of 30% literacy in the late 15th century.

Moran's article is the only one that I found which provides numerical estimates of literacy in England in 13-15th centuries. She notes, however, lack of extant records and bases her estimates on availability of schooling (making the numbers less reliable, at least according to O'Day).

Some of Moran's research results are summarized by O'Day as follows:

From this source [availability of schooling] she concludes that some 15% of the population of York diocese attended a school in the late 15th century, as compared with perhaps 9% in the early 15th century and some 4.7% in the late 14th century. But it may be suspected that these figures err considerably on the generous side. Dr. Moran based these estimates on calculations which assumed a regular and constant size for the schools concerned. Later evidence suggests that consistency in this respect was not a feature of early schools.

From reading Cressy's book, I think, I found the original source of the claim that about half of English population by the end of 15th century was literate. He attributes the number to Thomas More:

Cressy then proceeds:

While Cressy's book contains mass of numerical data related to literacy (based on various archival work), it is all broken into subcategories according to occupation and geography and, in the book, I could not find aggregate overall numbers. But, in his later paper, from 1993, "Literacy in context: meaning and measurement in early modern England", Cressy writes:

Thus, according to this estimate, the rate of literacy in mid-16th century England was about 12.5%.

Another estimate (dealing with the end of the medieval time and, thus, closer to the OP), based on the signage records appears in

Adam Fox, "Oral and Literate Culture in England, 1500–1700." Oxford University Press, 2000.

Based on the early arguments from Schofields 1973 article (which is widely cited and described as the breakthrough leading to transition from qualitative to quantitative estimates in literacy during early modern times), Fox then estimates that these numbers should be doubled to get an estimate of the reading capacity, thus, getting:

10% adult male reading and 2% adult female reading in England in 1500.

Lastly, regarding criticisms of usage of signage as a mean of estimating rates of literacy (ability to read) in late medieval/early modern times:

1. In their books O'Day, Cressy and Houston analyze in detail other available methods, note merits and demerits of each and, in the end, conclude in favor of signage. (This again follows Schofield's 1973 article.) In particular, they do discuss arguments similar to the one in Adam Baker's comment below, suggesting that for some people signing with a symbol/picture instead of the written name was a choice rather than the result of illiteracy. Reproducing these arguments here would take too much space and my answer is already too long, so I will refrain from doing so.

2. I am unsure about the origin of the claim that (generically) women were prohibited from "signing anything." I do not exclude that this was indeed the case in some places and at certain times. However, as fas as late medieval/early modern England goes, the claim is plain wrong. For instance Cressy documents striking difference in signage among women in London and elsewhere by the late 17th century: The percentage for both categories started near zero in 1500 and increased only to about 20% outside of London by the late 17th century. At the same time, in London, it reached about 50% by late 17th century. As far as I can tell, this dynamics completely invalidates the conjecture that women (at least in the discussed time period) were prohibited from signing their names.

Ditto the numbers provided by Houston in his article and the book for other parts of Europe: They indicate slow (but uneven) growth of female literacy (as measured by name signage) elsewhere in Europe, indicative of improvement of education rather than abolishing of some laws prohibiting signage.