I can give you some information on parts of the armed forces of the kingdom of Norway around 1270. At this time the population was somewhere between 300 and 500 thousand.

In this period Norway had two main "branches" of their "army". The first was a system known in norwegian as the "Leidang" this consistet of farmers and craftsmen that was called on by the king to help fight in wars and conflicts. The "leidang" did have small amounts of training, but acourding to "Gulatingsloven" the farmers that was a part of the "leidang" was obligated to train at least once a year. The "leidang" was mostly defencive force although they did most likely serve in multiple offensive campaigns as well.

The other "branch" was the "hird". The hird was the kings bodyguards and also was responsible for collecting taxes and managing the royal estates around the country. Parts of the hird did nothing to serve the king in peacetime and stayed on their own farms, until the king called on them to fight his wars. In exchange for their sevice they recieved gifts( weapons, jewelry, etc.) They had military training and was also sworn to the King. They was therefore the most valuable part of the armed forces.

Sadly i do not have any numbers on the amount of men in the "hird", but acourding to this site (managed by people with good qualifications) the hird had in the begining small numbers, but was expnaded at several occurances.

Acourding to the homepage of the Norwegian Armed Forces' museums the "leidang" consisted of 309 ships with in total 6 770 thwarts, with 4 men on each thwart, that would be 27 080 men. Now that you have these numbers it is important to note that this was not a standing army and that the whole leidang was, most likely, never used at the same time. (The wepsite have a interesting map that you may want to look at, it shows how the country was divided in and how many ships each part had too send)

Given this information i would say that at the most the king could probably levy at the very most 35 000 men, but more likely 30 000 thousand and maybe 380 ships. Altough these numbers are uncertain since i have no numbers on the "hird". Again that was most likely never done since only parts of the "leidang" was levied at any given time. I will also say that the website of the Norwegian Armed Forces' museums claims that this was a large amount in comparison to the rest of Europe.

In the end sorry for my bad english, and that all my sources is in norwegian, i hope google translate can help you if you want to read more. If something is unclear, both in my answare and in my sources please ask and i will gladly try to help make it clearer.